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Literature Review and Recommendations: Assessing methods to improve nitrogen use efficiency in potatoes and

selected cole crops.

30 March 2005

Written by: Laura L. Van Eerd, Ph.D., P.Ag. Ridgetown College, University of Guelph Ridgetown, ON N0P 2C0 Phone Number: 519-674-1644 Fax Number: 519-674-1600 E-mail Address: lvaneerd@ridgetownc.uoguelph.ca

Submitted to: Christoph Kessel and Donna Speranzini Ontario Ministry of Agriculture and Food

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1. EXECUTIVE SUMMARY Potato and cole crop nitrogen (N) fertility research and alternative nitrogen management strategies, such as optimizing N use efficiency (NUE) were reviewed. Best management practices (BMP) and current research needs were identified for Ontario production system which considers agronomic, economic, and environmental factors. There are many methods of calculating NUE but the crop, the harvested plant part, and the objectives of the research (i.e. soil versus crop focus) largely influences the appropriate NUE approach (Good et al. 2004). Generally, split N applications did not affect crop quality and provided little to no marketable yield advantage nor consistently improved NUE. There is very little evidence in the literature to suggest that N source, application timing, application method, or technology greatly improve NUE and/or minimize environmental N losses in potato or cole crop production. However, it may be possible to increase NUE through cultivar selection and breeding. For potatoes, BMPs which lower soil mineral N are preferred. Key to minimizing environmental N losses in cole crops is by implementing BMPs that capture mineral N as crop residues are mineralized. Current research needs among others include development and validation of a pre-sidedress N test (PSNT) and/or soil mineral N at planting to adjust N applications. The development of a vegetable production systems approach to optimizing NUE using different crop rotations should satisfy agronomic, economic, and environmental objectives.

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Table of Contents 1. EXECUTIVE SUMMARY .......................................................................................................................... 2

2. INTRODUCTION ....................................................................................................................................... 4

3. POTATOES................................................................................................................................................. 6 3.1. MANAGEMENT PRACTICES ....................................................................................................................... 6

3.1.1. Nitrogen source ............................................................................................................................... 7 3.1.2. Application timing ........................................................................................................................... 7

3.1.2.1. Impact on yield and crop quality.................................................................................................................. 7 3.1.2.2. Environmental impact................................................................................................................................. 7 3.1.2.3. Nitrogen use efficiency ............................................................................................................................... 8

3.1.3. Application methods ........................................................................................................................ 8 3.1.4. Technology...................................................................................................................................... 9

3.1.4.1. Formulations and other products.................................................................................................................. 9 3.1.5. Cultivar selection............................................................................................................................. 9

3.2. CONCLUSIONS ....................................................................................................................................... 11 3.3. RECOMMENDED BEST MANAGEMENT PRACTICES ..................................................................................... 12

4. COLE CROPS ........................................................................................................................................... 13 4.1. MANAGEMENT PRACTICES ..................................................................................................................... 13

4.1.1. Optimal N rates ............................................................................................................................. 13 4.1.1.1. Impact on yield..........................................................................................................................................13 4.1.1.2. Impact on crop quality ...............................................................................................................................14 4.1.1.3. Environmental impact................................................................................................................................15 4.1.1.4. Nitrogen use efficiency ..............................................................................................................................17

4.1.2. Nitrogen source ............................................................................................................................. 17 4.1.3. Application timing ......................................................................................................................... 18

4.1.3.1. Impact on yield and crop quality.................................................................................................................18 4.1.3.2. Environmental impact................................................................................................................................19 4.1.3.3. Nitrogen use efficiency ..............................................................................................................................19

4.1.4. Application methods ...................................................................................................................... 19 4.1.4.1. Impact on yield and crop quality.................................................................................................................19 4.1.4.2. Environmental impact................................................................................................................................20 4.1.4.3. Nitrogen use efficiency ..............................................................................................................................21

4.1.5. Technology.................................................................................................................................... 21 4.1.5.1. Pre-sidedress soil N test (PSNT).................................................................................................................21 4.1.5.2. Petiole sap quick tests ................................................................................................................................21 4.1.5.3. Fertigation.................................................................................................................................................22 4.1.5.4. Formulations and other products.................................................................................................................23 4.1.5.5. Modeling N uptake ....................................................................................................................................24

4.1.6. Cultivar selection........................................................................................................................... 24 4.2. CONCLUSIONS ....................................................................................................................................... 26 4.3. RECOMMENDED BEST MANAGEMENT PRACTICES ..................................................................................... 27

5. RECOMMENDED FUTURE RESEARCH.............................................................................................. 29 5.1. POTATOES ............................................................................................................................................. 30 5.2. COLE CROPS .......................................................................................................................................... 30

6. GENERAL CONCLUSIONS .................................................................................................................... 32

7. ABBREVIATIONS USED......................................................................................................................... 33

8. ACKNOWLEDGEMENTS....................................................................................................................... 33

9. REFERENCES .......................................................................................................................................... 33

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2. INTRODUCTION The intensification of agricultural production and increased pressure from society to protect consumers and the environment has facilitated the development of new Ontario legislation regarding nutrient management and drinking water source protection. As new nutrient management plans require producers to strictly adhere to provincial guidelines for nutrient applications, it may be more critical to match soil nitrate-nitrogen (NO3-N) with crop demand throughout the season in order to maintain crop yields and minimize environmental loss through leaching. Ontario vegetable producers have been relatively slow to modify nitrogen (N) fertilizer production practices according to nitrogen use efficiency (NUE) because of the need to validate and interpret scientific literature results in a manner that is useful to producers. Generally, much of the previous vegetable production research relied heavily on an agronomic and economic objective with little regard for the environment or nutrient use efficiency (Beegle et al. 2000). Clearly all these issues must be properly addressed if progress is to be made with respect to the development of best management practices (BMP) that improve the crop’s utilization of applied nutrients and/or bring about a reduction in the potential losses of nutrients to the environmental. For example, in Ontario cabbage studies, yield losses were estimated as high as $6,000 ha-1 between calculated yields at the most economic rate of N (MERN) and yields based on Ontario Ministry of Agriculture and Food (OMAF) recommended N rates (O'Halloran 1998a). Regrettably, higher N application rates for cabbage drastically reduced the overall NUE (< 30%) of the crop. Moreover, residual N left in the field after harvest often exceeded 200 kg N ha-1. If, in order to maintain crop yields and/or quality, these production systems require high N applications, which concomitantly results in excessive N losses, then the development of alternative management strategies will be crucial. These practices may include modifying nitrogen sources (urea, ammonium nitrate, calcium ammonium nitrate, calcium nitrate, etc), application timing (preplant vs split), application methods (broadcast, banded, incorporated, fertigation etc.), and/or technology (nitrification and urease inhibitors, soil and plant NO3-N quick tests). Moreover, the rate at which fertilizer N transformations occur in the soil after application can be altered by a variety of products and fertilizer formulations (e.g. urease inhibitors, nitrification inhibitors, slow release fertilizer formulations such as sulphur-coated, polymers etc.). There is potential that these technologies may offer increased yields and/or crop quality with less fertilizer applied and optimize NUE, thereby potentially minimizing environmental N losses. There has been significant research on the impact of different production practices on NUE worldwide. But the accuracy and understanding of this research from an Ontario vegetable production perspective needs to be critically evaluated in order to make BMP recommendations to Ontario potato and cole crop producers. There are many different definitions and methods for determining NUE and other related NUE indices (Table 1). There are four main differences in these calculations, which include: 1) inclusion of a zero N or low N control for comparisons and analysis or not, 2)

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estimates of soil supplied N compared to only N fertilizer applied, 3) plant weight versus yield weight and 4) plant or yield weights versus plant or yield N content. Often, NUE is the product of N uptake efficiency (NUpE) and N utilization efficiency (NUtE) (Table 1). Undoubtedly, the crop, the harvested portion, and the objectives of the research (soil versus crop focus) largely influences the appropriate NUE approach (Good et al. 2004). It is important to improve NUE and nutrient use efficiency of crop plants because of the economic costs of fertilization and the potential environmental damage of excessive fertilization (Good et al. 2004). However, it is critical that increases in nutrient use efficiency are not made at the expense of crop yield. If the global population reaches its estimated 9.1 billion people, there will be increased pressure to feed the world. Improving nutrient use efficiency may be one component of reaching this goal (Good et al. 2004) or it may adversely affect food production (Raun and Johnson 1999). This literature review analyzes scientific and grey literature from Ontario and other homoclimes and soil types on the effectiveness of different management practices to improve NUE in cole crops and potatoes. Moreover, the report provides recommendations on BMPs for Ontario potato and cole crop producers to minimize environmental N losses while maintaining crop yields and quality, which is especially important on sensitive soil hydrologic groups. It is anticipated that these recommended BMPs will meet the objectives of the public good with respect to soil, water and air quality while ensuring the Ontario agri-food sector remains sustainable and competitive on the global market. Finally, this literature review highlights areas where Ontario scientific research is warranted and which management practices should be further researched, developed and/or demonstrated.

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3. POTATOES

3.1. Management practices Generally, in potato, NUE decreases as the amount of available N increases (Kleinkopf et al. 1981) (Table 2 and 3). Overall, NUE (≈36%) did not vary with N application level (applied as a 1:1 split), genotype, or cropping year (Zvomuya et al. 2002). Increases in fertilizer N applications had no effect on vine N concentration (2.16%), but did linearly increase tuber N concentrations from 1.1% to 1.6% (Zvomuya et al. 2002). Moreover, N uptake in vines and tubers increased linearly as N application level increased (Zvomuya et al. 2002). However, yield increased with N rate in only one of two years. This research illustrates the difficulty of consistently improving overall NUE. In typical commercial New Brunswick potato fields, there was considerable variation in soil inorganic N available at planting between field and among years in the same field (Zebarth et al. 2003). For example, at planting, soil NO3-N ranged from 2 to 124 kg N ha-1 and soil NH4-N from 3 to 64 kg N ha-1 (Zebarth et al. 2003). The inorganic N at planting was either fertilizer N remaining from the previous crop or from nitrification during the spring (Zebarth et al. 2003); however it is difficult to estimate the proportion of fertilizer N. There was also large variation in potential losses of soil inorganic N between growing seasons (over the winter), which was highly dependent on precipitation and temperature (Zebarth et al. 2003). For example, spring soil NO3-N was between 3% to 100% of the NO3-N measured in the same field at harvest in the previous year (Zebarth et al. 2003). Therefore, assuming no nitrification between harvest and spring, there was between 0% to 97% losses in NO3-N. Fortunately, depending on the year only 12%, 19%, and 24% of all fields tested had NO3-N levels in excess of 100 kg N ha-1 at harvest (Zebarth et al. 2003). These fields tended to have high fertilization rates (≥200 kg N ha-1), but this was not true for all fields. Moreover, in a different study in Atlantic Canada the amount of mineral N accumulated in the nontreated plots (i.e. no fertilizer applied) was between 49 and 113 kg N ha-1 (Zebarth and Milburn 2003). Thus, in Atlantic Canada potato production, there was great variation in soil inorganic N at planting and at harvest and likewise high variation in potential environmental losses. It is very conceivable that similar variation NO3-N levels exist in Ontario, which illustrates the challenge of developing N fertilization recommendations and BMPs for all of Ontario. Residual soil N at harvest is generally considered available for loss over the fall and winter. However, there can be a high level of variation in the amount of N loss over this time period. For instance, N differences between winter and spring soil N levels on the same location over two winters was between 3.4 and 20.3% (Li et al. 1999). There was no corresponding increase in mineral N at deeper depths which suggests that either 1) the NO3-N leached below the sampling depth of 100cm or 2) leaching was not the major pathway of mineral N loss. Moreover, percent change in mineral N was not directly related to the amount of fertilizer N applied. For example the two highest changes in at-harvest versus spring mineral N (28% and 53%) were observed at fertilizer N rates of 70

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and 210 kg N ha-1, respectively. Unfortunately, N crop uptake and removal numbers were not obtained in this study (Li et al. 1999).

3.1.1. Nitrogen source To the best of author’s knowledge, there was no published literature on the effect of synthetic N source (urea, ammonium nitrate, calcium ammonium nitrate, calcium nitrate, etc) on potato NUE. Of the research summarized in Table 1, the majority (9 out of 17 manuscripts) of NUE research used ammonium nitrate as the N source. Furthermore, in 4 manuscripts, more than one N source was used in the experimental design, which suggests the authors’ perception that N source has little impact on NUE.

3.1.2. Application timing

3.1.2.1. Impact on yield and crop quality In one of three experiments, the split application (112 kg N ha-1) increased potato yield compared to a single application at planting (Joern and Vitosh 1995a). In a different study, in seasons with adequate rain-fed soil moisture, split applications had similar tuber size distribution and processing quality compared to preplant applications (Zebarth et al. 2004a; 2004b). In dry years, the split applications reduced tuber yield and size compared to preplant applications (Zebarth et al. 2004a; 2004b). Reducing N application levels at planting did not affect total yield but did lower culls and small sized tubers and increased larger tubers (Errebhi et al. 1998a). The observed lack of yield response to the split application in some studies (Li et al. 2003; 1999) was a result of the split application rate (140 kg N ha-1) being higher than the optimal N rate (70 kg N ha-1). Therefore one would not expect a yield advantage of applying more N above the optimal N fertilization. Overall, split N applications did not affect crop quality and had no consistent marketable yield advantage (Li et al. 2003; 1999; Vos 1997, 1999; Zebarth et al. 2004a; 2004b; Zebarth and Milburn 2003).

3.1.2.2. Environmental impact If heavy rainfall and/or excessive irrigation occur early in the season, application of high amounts of N at planting could lead to significant NO3-N leaching, even if the same total amount of N is applied throughout the season (Errebhi et al. 1998a). There was up to 50 days between planting and rapid crop N uptake, under typical New Brunswick conditions (Zebarth and Milburn 2003) during which the risk for NO3-N loss would be high. The actual loss of NO3-N during this time was dependent on weather, particularly excessive rainfall events. In fact, during the growing season, there was little evidence of NO3-N leaching (Zebarth and Milburn 2003). In fact, most NO3-N leaching in Atlantic Canada occurs in the fall and winter, which is similar to Ontario. Despite differences in fertilizer applied (0-200 kg N ha-1) and the timing of N applications, in two of three years of study, there were no differences in plant N accumulation or residual inorganic soil N at harvest (Zebarth et al. 2004a). Similarly, in one of two years of study, residual NO3-N at harvest was the same regardless of the

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amount of N fertilizer (0 - 135 kg N ha-1) applied at planting (Errebhi et al. 1998a). Therefore, in these studies there was no environmental benefit of split applications when the same total amount of N fertilizer was applied because splitting application just delayed when the losses could occur. It is likely that similar results would be observed in Ontario. Split applications had higher residual soil inorganic N at harvest compared to the equivalent amount of fertilizer N applied at planting (Li et al. 2003). Considering that tuber yield, plant N accumulation, and NUE were not different based on application timing (Li et al. 2003), the split application had either less N losses or immobilization during the growing season. Nevertheless, after harvest NO3-N would be susceptible to losses in the fall and winter. Therefore, because split applications do not increase plant N uptake (i.e. N removal from the soil), split applications only delay the potential risk of N loss to the fall/winter versus the spring for preplant N applications. Experiments with 15N-depleted fertilizer allow for the determination of what percentage of soil and plant N was derived from the fertilizer. In Michigan, regardless of timing and application amount, approximately 30-40% of applied 15N was not recovered and could have been in other plants or lost via leaching below 120cm, denitrification, and/or runoff (Joern and Vitosh 1995b). At harvest, approximately 27% of the applied 15N was found in the soil, most in the top 30cm. Moreover, >90% of 15N observed in the soil was in the organic form, regardless of fertilizer application timing and/or the amount applied. Most N studies do not have the ability to estimate N immobilization and organic N; therefore in calculated N budgets, unaccounted for N was assumed lost to the environment. Therefore, many studies may be overestimating the potential environmental losses of fertilizer N. It is possible that unaccounted for N could actually be immobilized and not immediately susceptible to leaching or denitrification. A specific portion of fertilizer 15N was immobilized into an organic form, regardless of timing and application N level (Joern and Vitosh 1995b).

3.1.2.3. Nitrogen use efficiency The N application amount and timing did not influence NUpE nor N partitioning in the plant (Joern and Vitosh 1995b). In a different study, in two of four years, crop N uptake and removal either increased by 10% or was not different in the split compared to preplant applications (Vos 1997, 1999). In one of two years of another study, total plant N accumulation decreased and NUE increased with reduced preplant N rates (Errebhi et al. 1998a). In other studies, no increase in NUE was observed with split application compared to preplant applications (Joern and Vitosh 1995a, 1995b; Li et al. 2003; 1999). Therefore, split applications did not consistently increase NUE in potato production.

3.1.3. Application methods According to common management practices, most (15 out of 17) NUE studies characterized in Tables 2-3 were banded N applications. No potato research was found in the literature which investigated the effect of different application methods on NUE.

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3.1.4. Technology

3.1.4.1. Formulations and other products The impact of a non-ionic surfactant on increasing NUE was evaluated based on the premise that the surfactant would minimize the presence of a dry zone in the potato hill and thus facilitate N uptake throughout the growing season (Kelling et al. 2003). There was no difference between nontreated and surfactant-treated plots with respect to total yield and US#1 yield. In one of the two years, crop N removal (i.e. tuber N content) and NUE were higher with surfactant compare to no surfactant, but only at the two higher N application rates (202 and 269 kg N ha-1). There may be potential to use non-ionic surfactants to increase N crop recovery (Kelling et al. 2003), however results were variable in the two year study. The use of nitrification inhibitors, such as nitrapyrin and dicyandiamide, and slow release N fertilizers, such as isobutylidene did not increase marketable tuber yield on irrigated sandy soil (Hendrickson et al. 1978; Martin et al. 1993), except in a year where rapid leaching of soil N was observed (Martin et al. 1993). Although soil NH4-N and NO3-N values were not determined, it was assumed that increased yield was a result of reduced NO3-N leaching (Martin et al. 1993). The use of nitrapyrin, a nitrification inhibitor, on irrigated loamy sand soil caused a predominance of NH4-N, which likely interfered with plant metabolism and reduced both total and marketable tuber yield (Hendrickson et al. 1978). Similarly, greenhouse grown potatoes yielded lower when fed 100% NH4-N compared to 100% NO3-N or 50% split (Serio et al. 2004). Moreover, on sandy soil with high porosity and low organic matter, nitrapyrin persistence was likely limited due to volatilization and hydrolysis under high temperatures (Hendrickson et al. 1978). Thus, although nitrification inhibitors reduce NO3-N soil levels and potential leaching, the negative impact on yield limits the adoption of this technology. Preplant application of polyolefin-coated urea (POCU) increased marketable yield by 3.3 tonne ha-1 compared to split application (1:1 planting:hilling) of urea (Zvomuya and Rosen 2001). Unfortunately, preplant application of urea was not conducted (Zvomuya and Rosen 2001), therefore a direct comparison of POCU and urea N source on potato yield was not possible because the experiment was confounded by application timing. Regardless, due to the expense of POCU net return was better for the split urea application despite lower yields (Zvomuya and Rosen 2001).

3.1.5. Cultivar selection Potato cultivars responded differently to N and have different optimal N application rates (Arsenault and Malone 1999). Early-maturing potato cultivars have lower NUE, NUtE (Zebarth et al. 2004c), and plant N uptake (Zvomuya et al. 2002) than mid-season or late-maturing cultivars. Despite differences in these NUE indices, soil NO3-N at harvest varied with cultivars but did not relate to date of maturity (Zebarth et al. 2003; 2004c). In an other study, although there were differences among early- or mid-season cultivars versus late-maturing cultivars with respect to NUE and yield, the trends were not consistent for the date of maturity (Kleinkopf et al. 1981). For some cultivars NUE was

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extremely variable depending on the growing season and for other cultivars NUE was relatively consistent (Errebhi et al. 1999). Overall, there was more variation in NUE between years compared to differences between cultivars and/or maturation (Zebarth et al. 2004c). Differences in NUE were observed in cultivars based on factors other than the length of maturity. The NUE of a cultivar can change considerably with different fertilization levels. The ‘NewLeaf Superior’ clone had a higher NUE and yield at lower N fertilization compared to ‘Superior’ (Zvomuya and Rosen 2002). In contrast, at higher N fertilization levels, ‘NewLeaf Superior’ had lower NUE and yield compared to ‘Superior’. It is clearly possible to increase NUE through cultivar selection and breeding (Errebhi et al. 1999; Errebhi et al. 1998b; Kleinkopf et al. 1981; Zebarth et al. 2004c; Zvomuya and Rosen 2002; Zvomuya et al. 2002). However, NUE varies greatly with growing season (Errebhi et al. 1999; Zebarth et al. 2004c), fertilization level (Zvomuya and Rosen 2002), and cultivar/clone (Kleinkopf et al. 1981). Given this and the observation that soil inorganic N concentrations at harvest did not relate to NUE or maturation (Zebarth et al. 2003; 2004c), it is unlikely that NUE is an appropriate tool for determining optimal N fertilization levels or for the prevention of environmental losses.

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3.2. Conclusions Application timing and method, N source and different technologies do not consistently increase NUE, improve yields, or minimize environmental losses. Overall, in the literature, there was very little variation in crop N uptake, removal and residue values (Table 3), which suggest little opportunity to improve NUE through crop N accumulation. The average NUE of data reported in Table 3 was 48% (standard error = 4.8). One method to estimate risk of environmental N loss was to compare crop N uptake or for an even more conservative estimate crop N removal, with fertilizer N application level. For example, there was only a 13 kg ha-1 difference between crop N removal and fertilization in potatoes with the optimum application of 134 kg N ha-1 (Tyler et al. 1983). Based on data presented in Table 3, only 6 out of 27 reported values had a difference between N fertilizer application and crop N removal greater than 80 kg N ha-1. Moreover, there were an almost equal number of cases (7 out of 27) where crop N removal was greater than fertilizer applied. With an average crop removal of 3.1 kg N per tonne of yield at a potato yield of 40.7 t ha-1 and an N application rate of 175 kg N ha-1, the difference between N input and output was 50 kg N ha-1 (Table 3). There are a number of questions that arise. What is the acceptable level of N losses to the environment? What is the acceptable level based on? Is 50 kg N ha-1 acceptable? And how or does this acceptable level change with soil hydrological groups with high leaching potential? Is the risk the same for losses do to denitrification or leaching? Clear and defined answers to these questions must be provided as nutrient management legislation impacts potato producers.

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3.3. Recommended best management practices BMP 1. Application rate of 150-175 kg N ha-1. Based on the literature, this

review paper, and information provided in Tables 2 and 3, an N application rate of 150-175 kg N ha-1 is recommended, which should be banded at planting. This recommendation is similar to current OMAF recommendations of 135-200 kg N ha-1 for expected marketable yields of 25-30 t ha-1 (OMAF 2004-2005). However, if the expected yield is 15 t ha-1 then OMAF recommends 50 kg N ha-1. The recommended rate of 150 to 175 kg N ha-1 is based on optimizing yields and does not ensure environmental protection. Appropriate N rates with BMPs listed below may lower environmental risk under typical Ontario conditions.

BMP 2. Banded N application. It is standard practice to band N applications.

This was typically method used in the research reported. Therefore, all N applications should be banded on either side of the seed/plant.

BMP 3. Preplant or split application. There was little to no benefit to split N

application of the same amount of N fertilizer because split applications do not consistently 1) provide a yield benefit, 2) improve NUE, or 3) reduce NO3-N quantities at harvest. From a BMP perspective, the main potential environmental benefit of split applications would be if the second application was not applied, thereby reducing the total fertilizer application.

BMP 4. No advantage of N technology products. Despite the potential

benefit of the aforementioned technology (nitrification inhibitors, slow release formulations, etc.) in wet years, use of these products is not justified because of the added cost and limited yield advantage. Moreover, at the time of preplant N application, it is practically impossible to predict ‘wet’ years when these technologies may be the most beneficial.

BMP 5. Reduce N application for early maturing cultivars. Differences in

NUE and optimal N application levels between cultivars and date of maturity indicate that different N recommendations should be used (Kleinkopf et al. 1981). A general BMP of reducing N applications by up to 50 kg N ha-1 for early maturing varieties is recommended. The proposed BMP is similar to OMAF’s recommended 70 kg N ha-1 for early varieties grown on mineral soil (OMAF 2004-2005). No other districts recommend N application according to cultivar or date of maturity (Table 7). Functionally, the difference in application rates between cultivars of 50 kg N ha-1 would be insignificant in light of year to year variation in N response and compared to the accuracy with which N is applied. Moreocer, adoption of this BMP by producers may be limited.

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4. COLE CROPS

4.1. Management practices

4.1.1. Optimal N rates In North America, cole crop fertilizer recommendations were developed based on experimentation and experience and range from 61.5 – 336 kg N ha-1, with a mode of 111 and 224 kg N ha-1 for low and high recommendations, respectively (Table 8). In Europe, cole crop fertilizer recommendations in different countries are based on relatively simple look-up tables and experience to adjustments to N rates based on spring Nmin to complex computer models (Rahn et al. 2001a). Despite differences in complexity, based on different field characteristics, there was good agreement between different European countries in their recommended N fertilization level for cauliflower; the majority recommending between 200 and 250 kg N ha-1. Cole crop response to increasing N applications has been described by the following models: quadratic, quadratic plateau, linear, linear exponential, or linear plateau (see Tables 5 and 6). For cauliflower, the linear plateau best described and estimated optimal fertilizer applications of pooled and individual data from seven site-years (Everaarts and van den Berg 1996). The linear plateau model considers the linear relationship between optimum fertilizer application and Nmin at planting and the quantity of N applied above which yield does not increase (i.e. the plateau).

4.1.1.1. Impact on yield Undoubtedly, cole crop yields increased with increasing N fertilization rates (Table 5 and 6). In the majority of experiments, there was a linear response of yield to N rates (Table 5 and 6), which suggest that the experimental N rates tested were not high enough to inhibit growth and that cole crops are very tolerant of excessive N. For Ontario broccoli production, calculated MERN values were between 297 and 312 kg N ha-1 (Bakker 2005). Zebarth et al. (1995) estimated the most profitable N rates for broccoli were between 395 and 508 kg N ha-1 depending on the time of planting and the year. However, lowering N application rates to 244 – 302 kg N ha-1 reduced broccoli yields by 0.5-1 t ha-1, while providing acceptable residual NO3-N at harvest level of 100 kg N ha-1 (Zebarth et al. 1995). Under fertigation, maximum cauliflower yield of No. 1 grade curds maximized at 292 and 400 kg N ha-1 depending on the year (McKeown and Bakker 2005b). Unfortunately, total marketable yield was not reported. Typically smaller heads (i.e. lower grade heads) were observed with lower N rates (Lisiewska and Kmiecik 1996; Rather et al. 1999; Thompson et al. 2000a). Therefore, in McKeown and Bakker’s (2005b) research, one would expect that maximum total marketable yield for cauliflower would be observed at lower N rates compared to rates needed to obtain No. 1 grade heads.

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Optimal N fertilizer application for cauliflower production in the Netherlands was 224 – Nmin (0-60cm) kg N ha-1 (Everaarts and De Moel 1995). In one of two years there was no differences in cabbage yield (Westerveld et al. 2004). In the other year, the zero N treatment had lower yields compared to all other treatments. In both years, there were differences in petiole sap N concentrations but high yields in low and high N rates suggest adequate soil N was present regardless of N fertilization. In contrast, on a clay loam site MERN values for cabbage were obtained at 349-406 kg N ha-1, however, MERN values were lower on lighter soil due to fertilizer toxicity (O'Halloran 1997, 1998a, 1998b). With fertigation, maximum cabbage yield was obtained with the highest N rate tested, 400 kg N ha-1 (McKeown and Bakker 2005a). The aforementioned cabbage studies were all conducted in Simcoe, Ontario. Likely weather, soil N mineralization, and other factors contributed to the observed differences in cabbage N response. In British Columbia, cabbage yields were calculated to maximize at 635 and 609 kg N ha-1, depending on the year with MERN values estimated at 5 and 2 kg N ha-1 lower, respectively (Zebarth et al. 1991). Optimal N fertilizer application for cabbage production in the Netherlands was 330 – 1.5Nmin (0-60cm) kg N ha-1 (Everaarts and Booij 2000). Overall, the applicability of MERN analysis of cole crops and likewise in many other vegetable crops was limited due to the 1) low cost of nitrogen fertilizer relative to total production costs, 2) relatively large price for the crop, and 3) the large variation in price during and between seasons (Everaarts and De Moel 1995; Everaarts and van den Berg 1996). For the aforementioned reasons, in most cases (see Tables 5) the MERN was typically very close to N rates required for maximum yield.

4.1.1.2. Impact on crop quality Nitrogen fertility had no affect on cole crop maturity in some studies (Kowalenko and Hall 1987a; Rather et al. 1999; Zebarth et al. 1995). In other studies, broccoli (Bakker 2005; Kahn et al. 1991; Lisiewska and Kmiecik 1996) and cauliflower (Lisiewska and Kmiecik 1996) maturity was delayed by at least five days with increasing N rates. In summer cabbage in one of two years, maturity of summer cabbage was delayed by three weeks at low N rates (Westerveld et al. 2004). The difference between cabbage and broccoli or cauliflower may be due to differences in plant growth stage when these crops are harvested. With respect to broccoli crop quality, the level of N fertilization had a different effect on crop quality depending on which parameter was measured. For instance, increasing N rates applied to broccoli decreased the number of misshapen heads and floret colour improved, but increased the incidence of hollow stem and head rot (Bakker 2005). No consistent relationship was reported between N fertilization rate and broccoli soft rot and hollow stem (Zebarth et al. 1995). In an Arizona fertigation study, increasing N rates had no effect on the incidences of hollow stem and discoloration (Thompson et al. 2002a). Similarly, N rates had no effect on storage quality of broccoli (Toivonen et al. 1994). Broccoli head weight and diameter (Kahn et al. 1991; Lisiewska and Kmiecik 1996; Thompson et al. 2002a; Toivonen et al. 1994) as well as NO3-N in the head

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(Bakker 2005; Lisiewska and Kmiecik 1996) increased with increasing N rates. For bunching broccoli, which have significantly smaller head size, optimal yield were achieved at lower N rates (125 – 250 kg N ha-1) (Toivonen et al. 1994). However, weather conditions had a larger impact on broccoli quality than N rate (Toivonen et al. 1994). Generally, cauliflower head size and weight were increased with increasing N fertilization (Lisiewska and Kmiecik 1996; Rather et al. 1999; Thompson et al. 2000a). In an Ontario fertigation study, in one of two years the incidences of ‘ricey’ heads was highest at the two lowest N rates (0, 68.5 kg N ha-1). In an Arizona cauliflower irrigation trial, ricey head, discoloured heads, as well as hollow and green stem were not affected by N rate (Thompson et al. 2000a). Likewise, defect bracting, malformed and ricey heads, and other curd characteristics such as colour, depth, density, or smoothness were not influenced by N availability (Rather et al. 1999). Cauliflower quality parameters such as loose and buttoned heads all increased when N was limiting (Rather et al. 1999). N application rates did not influence the storage quality of cabbage or yield losses due to disease (O'Halloran 1998b). The number of small or underdeveloped cabbage heads decreased with increasing N fertigation (McKeown and Bakker 2005a). Similarly, Chinese cabbage head size increased with increasing N fertilization (Warner et al. 2004). Although there was yearly variation, the incidence of bacterial soft rot and petiole spotting generally increased linearly and curvilinearly, respectively, with increasing N fertilization (Warner et al. 2004). In Denmark, in white cabbage, increased fertilization resulted in higher N removal and NO3-N content but lower dietary fiber and vitamin C content (Sorensen 1999). Regardless of the cole crops, for different quality parameters there was considerable variation between site-years (Kahn et al. 1991; McKeown and Bakker 2005b; Toivonen et al. 1994; Warner et al. 2004). This indicates that growing conditions, more than N rate strongly influenced cole crop quality (Toivonen et al. 1994). Therefore, by considering total marketable crop yield when determining optimal N rates, the specific and variable quality components would be intrinsically factored in.

4.1.1.3. Environmental impact Despite high N applications (up to 400 kg N ha-1), at harvest there was no difference between N rates in soil mineral N, with the majority of mineral N was in the top 30 cm of soil (Bakker 2005). Similar results were observed in cole crops grown in British Columbia (Kowalenko and Hall 1987a) and Arizona (Thompson et al. 2000b, 2002b). In these studies and others (Table 5), total plant N accumulation typically exceeded or was similar to N applications, suggesting that plant N output was equal to or exceeded N input. Furthermore, Bakker (2005) observed little evidence to suggest significant N losses to leaching or denitrification in studies conducted at Simcoe, Ontario Low residual mineral soil N (10 kg N ha-1) observed at harvest in Brussels sprouts was due to high N uptake rate, which resulted in rapid depletion of soil N and therefore risk of environmental losses were minimal during season (Booij et al. 1993). Similarly, in

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British Columbia, inorganic soil N was less 15 kg N ha-1 at harvest for all N application rates (0 to 500 kg N ha-1) in one of two years (Zebarth et al. 1991). In the other year, at harvest inorganic soil N was highest (30 kg N ha-1) at the highest N application rate. Zebarth et al. (1991) estimated that approximately 1/3rd of fertilizer N was unaccounted for, regardless of N application rate applied to cabbage. It is not known if the fertilizer N was lost to the environment. Similarly, independent of N application rate between 25% and 35% of available N was unaccounted for in cabbage grown in the Netherlands (Everaarts and Booij 2000). In the aforementioned study, the proportion of unaccounted for N was not influenced by application method (banded vs. broadcast) or timing (preplant vs. split). Because there was little evidence of leaching and the unlikely potential that denitrification or volatilization would cause such substantial N losses, it is hypothesized that the unaccounted for N was either immobilized in cabbage roots or most likely in leaves shed from the plant prior to harvest (Everaarts and Booij 2000). The fact that very similar quantities of unaccounted for N were identified in different site-years suggests that unaccounted N was related to biological (i.e. microorganisms or plants) rather than environmental (i.e. temperature or moisture) processes. In other studies, fertilizer N not utilized by the crop was apparently lost due to leaching or denitrification, which at an application rate of 440 kg N ha-1 amounted to as much as 200-250 kg N ha-1 (O'Halloran 1997). At harvest, there was 420 kg N ha-1 of NO3-N to the 75cm soil depth at the highest N rate tested (625 kg N ha-1) (Bowen et al. 1999; Zebarth et al. 1995). Whereas NH4-N averaged 28 kg N ha-1 in two out of three experiments, and was significantly higher (200 kg N ha-1) in one experiment. Lower N application rates of 244 – 302 kg N ha-1 lowered residual NO3-N at harvest to 100 kg N ha-1, with estimated broccoli yield reductions of 0.5-1 t ha-1 (Zebarth et al. 1995). Clearly for broccoli production in British Columbia, optimal N rates have been selected which were considered agronomically, economically and environmentally sound. Thus, there is an environmental risk associated with the high residual N and low fertilizer recovery. For cole crops, crop residues form the single largest source of potential losses of N to the environment (Everaarts and Booij 2000; Everaarts et al. 1996; Everaarts and de Willigen 1999). For example, in Brussels sprouts, at a fertilizer application rate of 300 kg N ha-1, it was estimated that 260 kg N ha-1 would remain in the field as crop residues (Booij et al. 1993). In cabbage, at the optimal N rate (330 – 1.5Nmin (0-60cm)), soil and crop residual N were 40 and 113 kg N ha-1, respectively (Everaarts and Booij 2000). Likewise, in cauliflower, 50-80 and 100-120 kg N ha-1 were observed at harvest in soil and crop residues, respectively. In aforementioned cabbage and cauliflower studies, there was no evidence for N leaching during the growing season. Brassicacaea residues quickly break down and release inorganic N, which is available for loss over the winter. Clearly, BMPs must be developed that minimize N losses when the crop residues breakdown.

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4.1.1.4. Nitrogen use efficiency Overall, as fertilizer N input increases NUE of cole crops decreases (Table 5). Apparent fertilizer recovery in the aboveground portion of the broccoli plant decreased with increasing fertilization from 91% to 4% at 125 to 625 kg N ha-1, respectively (Zebarth et al. 1995). In a British Columbia cabbage study NUE was approximately 32%, which was independent of N application rate (0-500 kg N ha-1) (Zebarth et al. 1991). In this study, there was a curvilinear yield response to N rate and a linear response of head N uptake to N rate applied. In Brussels sprouts, NUE (i.e. based on total plant N accumulation) was over 90% and independent of the amount of nitrogen applied (Booij et al. 1993). The higher cabbage yields with higher N applications resulted in drastically reduced overall NUE (< 30%) in cabbage (O'Halloran 1997, 1998b). Average NUE based on research summarized in Table 5 for broccoli, cauliflower, and cabbage were 38%, 47%, and 22%, respectively. In Ontario grown broccoli, total N accumulation increased with increasing N rates and head N accumulation was at a maximum of 99 kg N ha-1 when 340 kg N ha-1 was applied, giving a NUE of 29% (Bakker 2005). Estimated NUE in fertigated cabbage and cauliflower was 60% and 24%, respectively (McKeown and Bakker 2005a, 2005b). Under conditions typical of British Columbia broccoli production, the apparent fertilizer NUE at the 250 kg N ha-1 rate was 63% and 24% in the aboveground plant portion and the broccoli head, respectively (Kowalenko and Hall 1987a). Based on a more environmentally responsible N application (244 – 302 kg N ha-1), NUE of broccoli varied between 30% to 46% depending on planting date and year (Zebarth et al. 1995). Although higher N applications increased total plant N concentration, the proportion of N in the broccoli head was not influenced by N rate but did change significantly (38% to 57%) in different years (Kowalenko and Hall 1987a). This suggests little opportunity to increase NUE based on crop N accumulation if yields do no increase. At low N application rates (0, 125 kg N ha-1) inorganic soil N was extremely low (NO3-N; 4 kg N ha-1) when broccoli inflorescences were initiating (Bowen et al. 1999). However, marketable yields 57-76% of maxima were obtained at low fertilization because of N translocation from leaves to the inflorescence, which ensures inflorescence development (Bowen et al. 1999). Translocation of N was not observed at higher fertilization rates. Therefore, Bowen et al. (1999) suggests that N applications can be reduced without compromising marketable yield because the plant can compensate for low soil inorganic N levels by translocating N from the leaves to the broccoli head. Furthermore, the root depth and distribution of Brassicaceae species facilitates N uptake from more than 2 m deep (Kristensen and Thorup-Kristensen 2004b; Thorup-Kristensen and Van Den Boogaard 1998; Van Den Boogaard and Thorup-Kristensen 1997).

4.1.2. Nitrogen source In a southwestern Ontario study, Chinese cabbage head size increased with increasing N fertilization (0-300 kg N ha-1) (Warner et al. 2004). In this study, head size was larger

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with ammonium nitrate compared to calcium nitrate and urea applications but only in one of five site-years. Compared to other N sources, calcium nitrate and urea, ammonium nitrate increased the incidence of soft rot. In contrast, severity of petiole spotting was higher for calcium nitrate compared to urea. Perhaps the higher incidence of disease with different N sources related to the large percent of immediately available NO3-N although this was not assessed. Regardless, growers can lower the incidences of the aforementioned diseases by choosing disease resistant cultivars such as Yuki and avoiding excessive N applications. This research indicates that a balance between yield, quality (disease) and environmental protection can be optimized. Another report found in the literature on N source and NUE was on spring cabbage grown under high tunnels in Poland (Rozek et al. 1999; Sady et al. 1998). Besides the limited use of high tunnels in Ontario cole crop production, the applicability of this research was limited because 1) the experimental design was confounded by different application methods used for different N sources (e.g. potassium nitrate applied broadcast and banded applications of urea and ammonium sulfate) and 2) N rates were based on Nmin therefore the amount of immediately available nitrate was different for each treatment. With little evidence in the literature to suggest that N source consistently impacts cole crop yield, quality, or environmental losses, the usefulness of altering N source to optimize NUE is limiting.

4.1.3. Application timing

4.1.3.1. Impact on yield and crop quality The impact of split applications on yield varied with soil type (O'Halloran 1998b). On a sandy loam soil, the MERN and yields were higher for the split compared to the preplant application (318 vs 234 kg N ha-1). Thus on lighter soils, high N applications can result in yield reductions likely due to ammonium toxicity early in the season, therefore there was a benefit of split applying N. In one of two years, the MERN and yields on a clay loam soil were slightly lower for the split compared to the preplant application (389 vs 406 kg N ha-1). There was no yield difference in split applications between 50 and 100 kg N ha-1 applied at transplanting (O'Halloran 1998a). Furthermore, cabbage losses from disease and during storage were not different in split or preplant N treated plants. The benefit in terms of yield and quality of broccoli were negligible in a four site-year study in Quebec (Bélec et al. 2001; Coulombe et al. 1999). Increasing N rates at the time of sidedress application (35 days after transplanting (DAT)) increased hollow stem incidences without a proportionate increase in yield (Bélec et al. 2001; Coulombe et al. 1999). Thus preplant applications were favoured. Similarly, when N was applied preplant, cabbage yield was twice as high compared to split or delayed N applications (Wiedenfeld 1986). Cauliflower (Everaarts and De Moel 1995) and cabbage (Everaarts and Booij 2000; Westerveld et al. 2004) yield was no different or decreased when N was split applied versus preplant applications. In contrast, cauliflower yields were higher in split versus preplant application of ammonium sulfate in a single site-year

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Californian study with an application rate of 100 kg N ha-1 but there was no difference between split versus preplant application of 150 kg N ha-1 (Welch et al. 1985a; 1985b). Therefore based on the aforementioned research, when yield and quality are considered there was little evidence to support split applications of N from an agromonic and economic perspective.

4.1.3.2. Environmental impact Similarly, from the literature, there is little evidence to suggest an environmental benefit of split applications. Bakker (2005) observed little evidence to suggest significant N losses to leaching or denitrification in broccoli grown in Simcoe, Ontario. In another Ontario study, downward movement of N varied over the three years, depending on rainfall events but there was no cabbage yield benefit of split applications (O'Halloran 1997, 1998a, 1998b). The split application compared to preplant applications of 300 kg N ha-1 had the same (6 kg N ha-1) or slightly higher (27 vs. 17 kg N ha-1, respectively) soil residual N at harvest depending on the site-year (Everaarts and Booij 2000). Similar results were observed in cauliflower (Everaarts et al. 1996). Therefore, if the same amount of N is applied, split applications just delay potential N losses to the fall.

4.1.3.3. Nitrogen use efficiency Nitrogen use efficiency did not increase in the split versus preplant N application (O'Halloran 1997, 1998a, 1998b). In Denmark, in one of two years, reduced preplant N applications and increased split N application resulted in higher cauliflower yield and lower soil residual N by 14 t ha-1 and 21 kg N ha-1, respectively, while maintaining yield quality (Van Den Boogaard and Thorup-Kristensen 1997). Nitrogen use efficiency was 23.8% and 26.2% when more N was applied preplant compared to later in the growing season, respectively. Thus, NUE increased in the split application in one year but there were no differences observed in the other year. Similarly, there was no differences in cabbage (Everaarts and Booij 2000) and cauliflower (Everaarts et al. 1996) crop N uptake at harvest with split versus preplant N applications, which suggests no differences in NUE.

4.1.4. Application methods

4.1.4.1. Impact on yield and crop quality In broccoli, yield was highest at the highest N application rate (270 or 225 kg N ha-1) (Letey et al. 1983). In this study, conventional preplant and sidedress N application yielded higher than injecting N in the irrigation water (Letey et al. 1983). In PEI, there were differences in response of broccoli, Brussels sprouts, and cabbage to different application methods (Sanderson and Ivany 1999). Broadcast, banded, or split (65:35) application method of 120 kg N ha-1 did not influence Brussels sprouts marketable yield. For broccoli, the split application yielded higher than banded application and yield from the broadcast method was similar to the other aforementioned methods. In contrast, cabbage yield was reduced in the banded application compared to the other methods. It is important to note that yields of all cole crops were higher when a higher application

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rate of 150 kg N ha-1 was broadcast incorporated (Sanderson and Ivany 1999). Similarly, in an Ontario cabbage study, split N applications (50:225 or 100:175 kg N ha-

1) and strip-banding N applications (50:175 kg N ha-1) did not increase cabbage yields compared to the broadcast application (200 kg N ha-1), which had a lower total amount of N applied (O'Halloran 1998a). In Texas, cabbage yields were similar when preplant N was banded or broadcasted (Wiedenfeld 1986). Likewise, there was no cauliflower (Everaarts and De Moel 1995) or cabbage (Everaarts and Booij 2000) yield advantage of banding versus broadcasting preplant N. The lack of yield advantage for banding application methods was likely due to the root distribution of cole crops. Nitrogen depletion by the cole crop tended to be similar at different distances from the crop row, which suggests a uniform root distribution of cabbage (Everaarts and Booij 2000) and cauliflower (Everaarts et al. 1996). In cabbage, there was equal distribution of roots in rows and between rows, even to a depth of over 2 m (Kristensen and Thorup-Kristensen 2004b). Similar root distribution were observed in other Brassicaceae species such as cauliflower (Thorup-Kristensen and Van Den Boogaard 1998) and fodder radish (Kristensen and Thorup-Kristensen 2004a). Consequently, placement of fertilizer N was not critical because of the wide and deep root distribution, which will capture N throughout the soil profile. Moreover, cole crops are luxurious N consumers with the ability to translocation N from leaves to the infloresence under N limiting conditions (Bowen et al. 1999). It is not surprising that application method had a minimal effect on yield.

4.1.4.2. Environmental impact In an Ontario cabbage study, the method of application did not influence plant N uptake, NUE or residual soil NO3-N (O'Halloran 1998a) (see section 4.1.1 and 4.1.3 for more details). No soil NO3-N or crop N uptake values were reported in the PEI broccoli, Brussels sprouts, and cabbage study (Sanderson and Ivany 1999). As mentioned previous, with higher yields with broadcast N application (150 kg N ha-1) compared to the lower yielding banding and split application one would expect 1) more plant total N uptake based on typical plant %N, 2) similar quantities of residual soil NO3-N at harvest due to the low N fertilizer rates used, and 3) more crop residues at harvest because higher yields are generally associated with larger plants, which would result in more total N in the crop residues. Compared to fertigation, there was more residual NO3-N (52 kg N ha-1) at harvest when the same amount of N was applied as 3 split banded applications (Letey et al. 1983). There were no significant differences in soil residual mineral N at harvest in cabbage (Everaarts and Booij 2000) and cauliflower (Everaarts et al. 1996) when N was banded compared to broadcasted. In cabbage, at harvest, in the soil top 30 cm mineral N was relatively low (6 or 25 kg N ha-1 depending on the site-year) when 270 and 255 kg N ha-

1, respectively, were applied. In these cauliflower (Everaarts et al. 1996) and cabbage (Everaarts and Booij 2000) studies, there was little evidence of N leaching during the growing season and the proportion of unaccounted for N was similar for both application methods. Hence, environmental risk was similar for the different N application methods.

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4.1.4.3. Nitrogen use efficiency Banding granular fertilizer along the crop row increased fertilizer N recovery compared to fertigation (Letey et al. 1983). The method of application did influence total %N in leaves of broccoli, Brussels sprouts, or cabbage sampled at initial reproductive stages (Sanderson and Ivany 1999). Leaf N analysis indicated that these cole crops were not N deficient at this developmental stage. However, generally higher %N was observed in the broadcast 150 kg N ha-1 treatment, which corresponded to the highest yielding treatment for all three cole crops. At-harvest plant N uptake, NUE, or soil N analysis were not reported in this study. Cabbage (Everaarts and Booij 2000) and cauliflower (Everaarts et al. 1996) crop N uptake was similar regardless of banding versus broadcast N application, which suggest similar NUE, although NUE was not reported. In an Ontario cabbage study, application methods (i.e. banded versus broadcasted) did not improve NUE (O'Halloran 1998a). Overall, application methods should not be considered as techniques to improve NUE.

4.1.5. Technology

4.1.5.1. Pre-sidedress soil N test (PSNT) A PSNT test was developed in New Jersey and surrounding states on double-cropped autumn cabbage that followed sweet corn. Cabbage transplanting occurred between 25 July and 15 August, with harvest in late October to early November. The PSNT level of 24 ppm was established as the critical value indicating the need for split N application (Heckman et al. 2002). At 14-21 DAT, additional N applications applied when PSNT values >24 ppm did not improve cabbage marketable yields compared to non-treated plots. Based on Cate-Nelson analysis, N applications of 135 and 180 kg N ha-1 were necessary when PSNT values were 1-9 and 10-16 ppm, respectively. Clearly, the adoption of PSNT will reduce unnecessary N applications, thereby reducing monetary inputs and minimizing environmental N losses. The applicability of the PSNT to Ontario spring-grown cabbage requires experimental validation.

4.1.5.2. Petiole sap quick tests At selected growth stages, there was good correlation between the quick tests, such as the SPAD® and Cardy® NO3

- meter, and certified laboratory results for summer cabbage (Westerveld et al. 2003). Although the SPAD chlorophyll meter did not prevent the excessive application of N in one of two years, there is potential to use the SPAD with an over fertilized control to schedule split application (Westerveld et al. 2004). Regardless, there was little agreement between the SPAD and Cardy NO3

- meter and cabbage yields in 2001 when there was no difference in yield at the different N rates tested (0 - 340 kg N ha-1) (Westerveld et al. 2004, 2003). Samples of broccoli petiole sap NO3

- concentrations taken before and after sidedress application indicated that the on-farm quick tools detected increased NO3

- concentrations (Bélec et al. 2001; Coulombe et al. 1999). There was a quadratic response of marketable yield to petiole sap NO3

- concentration which accounted for 51-64% of the variability (Coulombe et al. 1999). However, this data set included only 3 of 4 experiments. The regression analysis between marketable yield and sap NO3

- was

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not as strong when sampling was taken before split N application (Coulombe et al. 1999). Similarly, there was a linear or quadratic response of petiole NO3

- concentration at the time of broccoli inflorescence initiation and N application (Kahn et al. 1991). But in three of four site-years, there was no yield response at the N rates tested (up to 280 kg N ha-1). Despite good correlation between certified laboratory and on-farm tool results, this technology may be limiting because petiole sap NO3

- concentrations at the time of split application did not relate to yields.

4.1.5.3. Fertigation In Ontario, cabbage and cauliflower responded differently to fertigation when 50% N was broadcast incorporated pre-transplant and the remainder N applied as 5 fertigation splits (McKeown and Bakker 2005a, 2005b). Cauliflower yield of No. 1 grade curds was highest at 292 or 400 kg N ha-1 depending on the year. However total marketable yield was not reported. Cabbage yields were maximized at the highest rate tested (400 kg N ha-1). Generally ricey cauliflower heads and undeveloped broccoli heads decreased with increasing N rate. Under fertigation, 200 and 400 kg N ha-1, NUE of cabbage was similar at 60.3% and 61.5%, despite large differences in yield 35 and 100 t ha-1, respectively (McKeown and Bakker 2005a). In contrast, cauliflower NUE of 23.5% and 45% was observed with application rates of 200 and 400 kg N ha-1 but with similar cauliflower yields of 27 and 23 t ha-1, respectively (McKeown and Bakker 2005b). Therefore, cabbage was a luxurious consumer of fertilizer N, with plant N accumulation exceeding N application (i.e. plant N accumulation of 286 and 415 kg N ha-1 at application rates of 200 and 400 kg N ha-1, respectively). In contrast, in cauliflower, plant N accumulation was similar regardless of the amount of N applied (i.e. plant N accumulation of 226 and 254 kg N ha-1 at application rates of 200 and 400 kg N ha-1, respectively). This suggests a potential loss of 146 kg N ha-1 at the high N rate. At harvest, the average residual NO3-N was 27-38 and 25-45 kg N ha-1 for cabbage and cauliflower, respectively for application rates of 0-400 kg N ha-1 (McKeown and Bakker 2005a, 2005b). Similar residual NO3-N at harvest for plots receiving 0 or 400 kg N ha-1 suggests that either 1) the plants receiving N fertilizer have taken up most of NO3-N and depleted the soil to levels similar to the non-treated plants; as was the case for cabbage or 2) there was significant losses of available NO3

-, either through leaching, denitrification, or immobilization in the treated plots during the growing season resulting in similar residual N; the likely explanation for cauliflower. In Denmark, it is estimated that a 100 kg N ha-1 increase in N supply (fertilizer N plus Nmin) resulted in more N in harvested cauliflower (15 kg N ha-1), soil (17 kg N ha-1), and crop residues (52 kg N ha-1) (Van Den Boogaard and Thorup-Kristensen 1997), suggesting 10 kg N ha-1 was unaccounted for. Thus, the majority of N was in crop residues. Likewise, the amount of N in the crop residue was 94 and 174 kg N ha-1 for cauliflower and cabbage, respectively (McKeown and Bakker 2005a, 2005b). Therefore, BMPs that consider the management of N from crop residue is important when considering potential environmental losses.

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In Arizona, when agronomic, economic, and environmental factors (i.e. ≥95% of maximum yield and ≤40 kg N ha-1 of soil residual N) were considered the optimal or near-optimal N rate was between 350-400 and 300-500 kg N ha-1 at a soil water tension of 10-12 and 10 kPa with subsurface drip fertigation of winter-seeded cauliflower (Thompson et al. 2000a, 2000b) and broccoli, respectively (Thompson et al. 2002a, 2002b). For winter broccoli production in Arizona, there was no difference in fertigation frequency (daily, weekly, bi-weekly, monthly) on total marketable yield (Thompson et al. 2003). In this fertigation study, as much as 39-41% and 42-46% of applied N was unaccounted in cauliflower (Thompson et al. 2000b) and broccoli (Thompson et al. 2002b), respectively and was presumably lost via leaching and/or denitrification. The highest amounts of unaccounted for N (i.e 293 and 230 kg N ha-1) for cauliflower and broccoli, respectively, occurred at the highest N application rates. Overall NUE generally decreased with increasing N rates in cauliflower; for instance 58% and 41% for application rates of 300-340 and 600 kg N ha-1, respectively (Thompson et al. 2000b). At high N rates (350 kg N ha-1) the frequency of fertigation did not impact broccoli NUE, but at lower N (250 kg N ha-1), the highest NUE was observed with bi-weekly fertigation (Thompson et al. 2003). For subsurface drip-fertigated broccoli, apparent NUE was 90 and 81% when 250 and 350 N ha-1 were applied (Thompson et al. 2003). Unfortunately, it is difficult to compare Ontario production to winter cole crop production in the Arizona desert. In this Arizona study, the breakdown of plant residues was not considered as part of the environmental impact. In Ontario, it is important that mineralization of plant residues be considered because of the humid temperate climate and the length of time between cole crop harvest and planting of the next crop.

4.1.5.4. Formulations and other products In two contrasting Texas growing seasons (i.e. cool and dry vs typical), there were no difference in cabbage yield when the following N sources and slow release N products were used: 1) water soluble forms; ammonium sulphate or ammonium nitrate, 2) sulphur-coated urea, and 3) methylene urea (Wiedenfeld 1986). In a single-year California study, application of the nitrification inhibitor, nitrapyrin, with ammonium sulphate increased yields of Brussels sprouts, cabbage, and cauliflower (Welch et al. 1985b) compared to ammonium sulphate alone (Welch et al. 1985a). In China, the use nitrification inhibitor DMPP (3,4-dimethylpyrazole phosphate) increased the marketable yield of cabbage in one of two years (Chao et al. 2004). At the same fertilization level (450 kg N ha-1), there were no differences in total accumulated plant N or NO3-N content between plants treated with or without DMPP. Therefore, in one out of two years NUE was higher when DMPP was used. Because of the year-to-year variation and the added costs the benefit of these technologies is considered limited. In Poland, over the course of a four year rotation (cabbage, onion, red beet, cabbage), the one time application of 1000 kg N ha-1 was applied as a slow release fertilizer (dissolving coefficients of 1.3% and 5% in a 1:1 mixture; no formulation or name was given). With one application, all four crop yields over the four year study were no different than yearly applications of ammonium nitrate or urea (150 or 200 kg N ha-1,

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depending on the crop) (Kolota et al. 1992). Unfortunately, soil mineral N was not determined, but because yields were higher with the slow release fertilizer than the non-treated control it is reasonable to assume that minimal N losses occurred over the four year study. Practically, the ratio of different dissolving coefficients could be modified to Ontario conditions, thereby providing a four year N supply with one application. However, the challenge may be to convince Ontario growers that adequate yields can be maintained 4 years after application. For instance, a grower might be tempted to apply additional N before the slow release N has been eliminated, which may result in large environmental losses.

4.1.5.5. Modeling N uptake In greenhouse studies, broccoli shoot dry weight and yield were increased by 10 and 58%, respectively by reducing N rates at inflorescence initiation (Nkoa et al. 2001; Nkoa et al. 2003). Although the direct applicability the greenhouse approach described by Nkoa et al. (2001) to field grown broccoli may be low, it clearly demonstrates the opportunity to increase broccoli NUE by matching plant N demand with supply. In field experiments, by determining plant N accumulation over the growing season it is possible to determine the rate and maximum amount of N uptake in relation to plant stage of development. Many researchers have followed this approach in broccoli, (Bakker 2005; Thompson et al. 2002a) and cauliflower (Alt et al. 2000; Everaarts 2000; Feller and Fink 1999; Kage et al. 2000; Thompson et al. 2000a). Ideally these models should be designed based on plant stage of development or growing degree days, rather than DAT to optimize the applicability of comparisons between seasons. More detailed models incorporate other data such as soil types, rainfall amounts, expected yields, light intensity, and many others to predict crop N requirements (Alt et al. 2000; Kage et al. 2003a, 2003b; Rahn et al. 2001b; Vågen et al. 2004). One such model, HRI WELL_N has been used by growers since 1994 (Rahn et al. 2001b). These models match soil N availability to crop N demand, which may be useful in scheduling N applications, particularly in fertigation.

4.1.6. Cultivar selection Cauliflower cultivars ‘White Empress’ and ‘Stovepipe’ had linear and quadratic responses, respectively, to increasing N rates but ‘White Empress’ overall yielded higher (Batal et al. 1997). Similar N responses were observed in two spring-planted collards cultivars (Dangler and Wood 1993). The difficulty with selecting vegetable, particularly cole crop, cultivars that have high NUE is due to the historic screening of cultivars based on yield potential under adequate N conditions. Rather et al. (1999) suggests that cultivars which are non-responsive to N inputs should be bred and selected for because this will ensure stable high yields under limiting and non-limiting N supply. For example, under N-limiting (zero fertilizer N) and –nonlimiting (fertilizer applied to N soil supply of 250 kg N ha-1) conditions three cauliflower cultivars were compared for yield and quality aspects (Rather et al. 1999). Compared to the other cultivars, ‘Marine’ was considered to have a high NUE because marketable yield was high under both N limiting and non-limiting soil conditions (see Table 1 for NUE definition). Using this method of cultivar selection protects growers from low yields and

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the corresponding low monetary returns if N becomes limiting (Rather et al. 1999). Furthermore, cultivars that can produce more plant biomass/yield for the same N input or conversely, produce the same biomass/yield under lower N conditions have the potential to minimize N losses to the environment by reducing overall N inputs or by removing more soil N (Rather et al. 1999).

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4.2. Conclusions Generally a linear response of cole crop yield to increasing N fertilizer indicates that cole crops are luxurious N consumers, which are seldom injured by excessive N. Similar to potatoes, there was very little variation in crop N uptake, removal and residue values (Table 5), which suggest little opportunity to improve NUE through crop N accumulation. The average NUE of data reported in Table 5 for broccoli, cabbage, and cauliflower were 38% (se = 7.7), 47% (se = 8.2), and 22% (se = 4.0), respectively. The difference in fertilizer N input and plant N accumulation based on data presented in Table 5, averaged 78, 111, 134 kg N ha-1 for broccoli, cabbage, and cauliflower, respectively. This represents considerable amounts of soil and particularly plant residual N in the field after harvest, which would be susceptible to leaching or denitrification losses. Based on OMAF research, there were considerable decreases in soil NO3-N quantified at harvest compared to in the spring (A. Verhallen; pers. comm.). Given the high N content in crop residues, there is potential for large quantities of N losses from cole crop production. To minimize N environmental losses, BMPs must be designed to minimize N losses after cole crop losses.

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4.3. Recommended best management practices BMP 1. Application rate of 250-300 kg N ha-1. Based on research reported on

in this literature review (Table 5), 250 to 300 kg N ha-1 is recommended for optimal cole crop production. Current Ontario recommendations for cole crop production are 130 kg N ha-1 for Broccoli, cauliflower, and Brussels sprouts and 170 kg N ha-1 for cabbage , with a suggested extra 40 kg N ha-1 sidedressed on sandy soils if rainfall is excessive (OMAF 2004-2005). This recommended rate of 250 to 300 kg N ha-1 is based on optimizing cole crop yields and does not ensure environmental protection. Appropriate N rates with BMPs listed below can lower environmental risk under typical conditions

BMP 2. Similar N rates for broccoli, cauliflower, and cabbage. Although

there are considerable differences between cole crops in yield, and plant N uptake, the impact of these differences on NUE does not warrant different recommendations for broccoli, cauliflower and cabbage. Broccoli, cauliflower, and cabbage yields of 19.5, 32.6 and 81.1 t ha-1, respectively would result in an estimated plant N accumulation of 300 kg N ha-1. These yields are not unusual for Ontario cole crop production. Thus, at the recommended rate of 300 kg N ha-1 fertilizer inputs have been shown to be very similar to crop N accumulation. Based on data presented in Table 5, average optimal N rates for yield of broccoli, cabbage, cauliflower, and Brussels sprouts was 282, 273, 243, and 147 kg N ha-1, respectively. Therefore, the recommended range of 250-300 kg N ha-1 encompasses three of four crops. There is not sufficient data on Brussels sprouts to base a recommendation for this crop. However, in Ontario (OMAF 2004-2005) and other regions in North America, N recommendations include Brussels sprouts with other cole crops (Table 8).

BMP 3 Broadcast application. Based on cole crop root growth and the lack

of yield advantage of other methods of application, broadcast N application with or without incorporation is recommended. There was little evidence in the literature to support adoption of other application methods.

BMP 4. Preplant or split application. There was little evidence of in-season

NO3-N leaching in the literature and in Ontario studies. Thus, there is little environmental benefit of split N applications. However, in Ontario, on lighter soil high preplant N applications did show reduced yields, likely due to ammonium toxicity (O'Halloran 1998a). Therefore on lighter soils split applications may be of economic benefit. It must be noted that in several studies, there was no yield benefit and in some instances a reduction in yield when N was split applied. From a BMP

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perspective, the potential environmental and economic benefit of split N applications would be if the second application was not applied, thereby reducing to total fertilizer application and the potential for environmental loss due to denitrification. Based on modeling of crop N uptake throughout the season in broccoli grown in Ontario, the most rapid N plant uptake occurs when plants were at the 8-11 leaf stage, approximately 20 to 30 DAT (Bakker 2005). Therefore, depending on application method and N source, split applications should be applied at the 6-8 leaf stage. Thus OMAF’s current recommendation of ¾ and ¼ N application preplant and 21 DAT (OMAF 2004-2005) is supported by the literature reviewed in this manuscript.

BMP 5. No advantage of N technology products. Similar to potatoes, the

potential benefit of the aforementioned technology (nitrification inhibitors or slow release formulations) in wet years was not sufficient to justify the added cost and limited yield advantage. Alternative N application strategies have not been widely adopted in cereal production largely because of the ease and affordability of applying more N than needed at or before planting (Raun and Johnson 1999). It is likely that the same is true for cole crop production. Regardless, no BMP can be recommended with regards to N source or technology because there is no evidence in the literature to suggest these production practices greatly improve NUE or minimize environmental N losses. Moreover, at the time of preplant N application, it is impossible to predict ‘wet’ years when these technologies may be the most beneficial.

BMP 6. Residue management. Cole crop residues quickly mineralize, which is

a concern for N losses to the environment in the fall and over winter. BMPs must be implemented that minimize N losses especially on hydrologically sensitive soils (i.e. group AA or A). Therefore, in order to significantly lower the risk of environmental contamination, the following BMPs are recommended:

1) On early harvested cole crops, cover crops should be planted and establish as soon as possible after harvest (Everaarts et al. 1996). However, there is often limited establishment of cover crops succeeding late harvested cole crops.

2) For late season harvests, a BMP to limit N losses through leaching would be to delay tillage and leave crop residues undisturbed through the winter (Wehrmann and Scharpf 1989). However, this may be of concern because of malodors.

3) Alternatively, cultivars that have a lower leaf-to-head weight ratio should be grown to reduce the amount of N in crop residues remaining in the field after harvest (Everaarts and Booij 2000).

4) Restrict production of late season/harvested cole crops on hydrologically sensitive soils. If autumn cole crops are grown then the majority of crop residues should be physically removal from the field (Everaarts and Booij 2000). Suggested uses for the residues include composting or feeding to livestock. Moreover, on hydrologically sensitive soils, early season cole crops must be cover cropped.

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5. RECOMMENDED FUTURE RESEARCH The following research has been identified as necessary based on gaps in knowledge and/or the need for validation in Ontario vegetable production systems.

1. Characterization of the fate and persistence of fertilizer N in vegetable crop production. Based on the results of Joern and Vitosh (1995a; 1995b) immobilization of fertilizer N may be underestimated and therefore losses to the environment via leaching and denitrification would be overestimated. Under Ontario vegetable field conditions, 15N studies should assess the fate and persistence of fertilizer N, with emphasis on partitioning into soil organic and inorganic fractions. This research should focus on potential N losses through the season, especially in relation to timing of split fertilizer applications. As well, the research should include characterizing NUE or fertilizer N recovery, and N partitioning within the plant. Ideally, these studies should follow N cycling through two growing seasons to better characterize N fate through season and over winter. It would be beneficial include two soil types. Anticipated results would provide information on the risk and pathway of N losses to the environment, which can then be used to develop BMPs.

2. Adjusting N fertilizer applications based on Nmin. For many years now,

determining Nmin at the time of planting has been successfully used in the European Union to adjust N fertilizer applications. For instance, a soil N supply of 250 kg N ha-1 (i.e. Nmin at 0-60 cm plus fertilizer N equals 250) was deemed optimal for cauliflower production (Rather et al. 1999). In this study, Nmin was between 20 to 116 kg N ha-1 at planting. Therefore fertilizer applications varied from 230 to 134 kg N ha-1 yet yields and crop N uptake did not vary significantly and plant N was deemed sufficient based on leaf N content. The applicability of using Nmin in Ontario vegetable production practices needs to be explored. Observations from research trials conducted in British Columbia (Zebarth et al. 1995) and Quebec (Bélec et al. 2001) indicate that Nmin determined at the time of broccoli transplanting provided a good estimate of N available to the crop during the growing season and was identified as an important factor when determining optimal N application. However, the aforementioned research did not focus on using Nmin to adjust N applications. Clearly, there is potential to use Nmin in Ontario, but adoption by growers will require considerable field research to optimize N rates according to Nmin.

3. Modelling N fertilizer needs. Detailed mathematical models, for example

HRI WELL_N (Rahn et al. 2001b)), have been designed to predict crop N demand and to direct growers on the optimize N fertilizer applications necessary. Future research should be initiated to validate HRI WELL_N or develop a similar model for use in Ontario vegetable production. There is opportunity to collaborate with Ontario Weather Network (OWN) to

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incorporate local weather data into models which predict N availability and crop demand. Ideally this model could be used by farmers as a decision tool for fertilizer applications which optimize yields and economic gains, while minimizing environmental N losses.

4. Validation of on-farm N status tests. The broad scale applicability of

petiole sap NO3-N quick tests may be limiting because petiole NO3

-N concentrations vary site-to-site and year-to-year, even at the same fertilization level (Bélec et al. 2001; Coulombe et al. 1999). It has been suggested that this limitation may be overcome by the inclusion of a over-fertilized zone within commercial fields to be used as a reference (Bélec et al. 2001). Bélec et al. (2001) and Coulombe et al. (1999) suggest that quick tests may be useful for the refinement of N fertilization during the broccoli growing season. More research is required to relate crop developmental stage to N concentration (Bélec et al. 2001; Coulombe et al. 1999). Therefore future research needs to examine the ability of on-farm quick N status tools (i.e. Cardy® meters, NO3-N test strips, SPAD® chlorophyll meter) to schedule split applications. Critical to this research is observed difference in yields at different N rates.

5.1. Potatoes Experimental design is critical for assessing the potential for split N applications to reduce total N application. In many of the potatoes studies summarized in Tables 2-3, the split application was either above the optimal N rate (Li et al. 2003; 1999), the same N rate applied preplant or split (Zebarth et al. 2004a; Zebarth et al. 2004b; 2003), or different N rates split in equal proportions (Joern and Vitosh 1995a, 1995b). Although these aforementioned studies were properly designed, the results do not adequately address the potential for split N applications to reduce total N application. Future potato research should focus on carefully designed experiments with the research objective of determining optimal split N applications to reduce total N application.

5.2. Cole crops 1. Development of a pre-sidedress soil N test (PSNT). Future research

should validate if soil N tests at time of transplanting and also at time of split application can be used to modify N application rates in Ontario. Validation of cabbage PSNT developed by Heckman et al. (2002) under Ontario conditions is required as well as the comparison of the cabbage PSNT for use in other cole crops. Following the design of Heckman et al. (2002), key to developing a new PSNT is compiling an extensive database with many trials (e.g. 40) over a number of growing seasons (e.g. 5). The PSNT would be an effective tool for farmers to determine the need for split N applications and provide guidance on the amount of fertilizer required. This would effectively reduce over application of N, thereby minimizing environmental losses. Based on results of an Ontario validated cabbage

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PSNT, other PSNTs should be developed for other vegetable crops, particularly those grown on hydrologically-sensitive soils.

2. Estimates of crop residue mineralization. Cole crop residues comprise

a significant portion of plant N accumulation (Table 5). For instance, increasing N supply from 150 to 400 kg N ha-1 resulted in increased crop residues from 90 to 221 kg N ha-1 (Van Den Boogaard and Thorup-Kristensen 1997). Due to a low C:N ratio (e.g. 16:1 for Brussels sprout leaves (Booij et al. 1993)), mineralization of cole crop residues is quick, leading to potential NO3-N losses over the fall and winter. There is a need to assess the extent and rate of mineralization of N from cole crop residues in Ontario under different management systems (e.g. incorporation, different soil types, cover crops, etc.). This research should also focus on identifying pathways of N losses through to the next growing season. It is anticipated that this research will lead to the development of BMPs that minimize environmental losses of N from cole crop production systems.

3. Adjusting C:N ratios to minimize N losses. One potential method of

immobilizing mineral N after cole crop harvest may be with the application of a carbon source such as paper mill or oily wastes (I.P. O’Halloran, pers. comm.). By balancing the low C:N ratio of cole crop plant residues with an application of a waste which has a high C:N ratio, it may be possible to immobilize N in microbial biomass. Future research should examine the applicability of using such wastes to immobilize N from cole crop residues in the fall and monitor N mineralization in the following spring. This could lead to the development of BMPs, which reduce contaminant loading into the environment from two sources; NO3-N from the field and paper mill and/or oily effluent wastes.

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6. GENERAL CONCLUSIONS Analysis of the literature confirms and validates much of current potato and cole crop production in Ontario, and highlights opportunities to reduce N inputs. Given increased pressure on agriculture from society to protect consumers and the environment, fertilizer N recommendations and BMPs must be based on agronomical, economical and environmental considerations. Generally, decreasing N fertilization and/or increasing plant N accumulation reduces NUE. From an environmental point of view, reduced N applications equate to reduced risk. Conversely, increasing plant N uptake does not necessarily result in less environmental N losses considering that N accumulated in cole crop residues may be rapidly mineralized and available for loss. The increased plant N uptake associated with increased fertilization often results in increased NO3-N in the edible portion of the crop. The health concerns of human consumption of excessive quantities of NO3 have been widely documented. The question arises, particularly from a vegetable perspective, should management practices that optimize NUE by increasing NO3-N content in the edible portion of the plant be encouraged? With increasing N fertilizer and other input cost, are BMPs that encourage optimal NUE sustainable. Is improving NUE really the correct goal producers should be aiming for? Perhaps a better goal would be to increase yields with reduced N inputs and minimal N loss. The long term impact of reducing N fertilization and thus NUE on principal soil parameters such as soil organic C needs to be considered. For instance, in winter wheat, higher N fertilization rates while decreasing NUE, increased long term soil organic carbon (Raun et al. 1998). Reducing N fertilization may have untoward effects on soil fertility in the long term. From a nutrient management perspective, knowledge of root growth and development in time and space can allow for vegetable cropping systems that maximize plant N uptake from different soil depths. A systems approach to nutrient management has the potential to minimize groundwater N contamination. Therefore, vegetable production systems BMPs should consider crop rooting depth within crop rotations to improve NUE of the system and minimize N losses by leaching (Kristensen and Thorup-Kristensen 2004b). The huge variation across years, soil characteristics, and management practices in soil NO3-N between harvest and the next spring (Zebarth et al. 2003) as well as at planting and at harvest, has serious implications for developing nutrient management strategies and recommendations. Large year-to-year variation in N cycling, not to mention the various weather and soil characteristics found in Ontario, makes it very challenging to make sweeping N recommendations which encompass agronomic, economic, and environmental objectives. The opportunity for growers to input data into software decision tools, such as NMAN, will take into account this variation and ideally provide for improved N management and reduced environmental risk on a farm-by-farm basis.

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7. ABBREVIATIONS USED BMPs, best management practices; DAT, days after transplanting; MERN, most economic rate of nitrogen; N, nitrogen; Nmin, soil mineral N concentration; NO3-N, nitrate-nitrogen; NUE, nitrogen use efficiency; NUpE, N uptake efficiency; NUtE, N utilization efficiency; OM, organic matter; OMAF, Ontario Ministry of Agriculture and Food; POCU, polyolefin-coated urea; PSNT, pre-sidedress soil nitrate test; SSC%, percent sand, silt, clay.

8. ACKNOWLEDGEMENTS The author gratefully acknowledges I.P. O’Halloran and J.W. Zandstra for their critical review and useful suggestions throughout the preparation of this manuscript. The assistance of M. Zink, M.A. Bulckaert, and B. Clark was appreciated. Funding for this manuscript was provided by the Ontario Ministry of Agriculture and Food.

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64. Rosen, C.J. 1990. Leaf tipburn in cauliflower as affected by cultivar, calcium sprays, and nitrogen nutrition. HortScience 25: 660-663.

65. Rozek, S., Leja, M., Wojciechowska, R., Sady, W. 1999. Nitrate and nitrite contents in spring cabbage as related to nitrogen fertilizer type, method of fertilizer application and to nitrate and nitrite reductase activity. Acta Horticulturae 506: 153-157.

66. Sady, W., Rozek, S., Leja, M., Mareczek, A. 1998. Spring cabbage yield and quality as related to nitrogen fertilizer type and method of fertilizer application. Acta horticulturae 506: 77-80.

67. Sanderson, K.R., Ivany, J.A. 1999. Cole crop yield response to reduced nitrogen rates. Canadian Journal of Plant Science 79: 149-151.

68. Serio, F., Elia, A., Signore, A., Santamaria, P. 2004. Influence of nitrogen form on yield and nitrate content of subirrigated early potato. Journal of the Science of Food and Agriculture. 84: 1428-1432.

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71. Thompson, T.L., Doerge, T.A., Godin, R.E. 2000b. Nitrogen and water interactions in subsurface drip-irrigated cauliflower: II. Agronomic, economic, and environmental outcomes. Soil Science Society of America Journal 64: 412-418.

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73. Thompson, T.L., Doerge, T.A., Godin, R.E. 2002b. Subsurface drip irrigation and fertigation of broccoli: II. Agronomic, economic, and environmental outcomes. Soil Science Society of America Journal 66: 178-185.

74. Thompson, T.L., White, S.A., Walworth, J., Sower, G.J. 2003. Fertigation frequency for subsurface drip-irrigated broccoli. Soil Science Society of America Journal 67: 910-918.

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Pag

e 39

of 6

0

Tabl

e 1.

Def

initi

ons

and

met

hods

use

d to

det

erm

ine

nitro

gen

(N) e

ffici

ency

indi

ces

in d

iffer

ent c

rops

. R

efer

ence

Te

rm

Cal

cula

tion

Def

initi

on

Uni

ts

Not

es

Nitr

ogen

use

effi

cien

cy in

dice

s in

PO

TATO

ES

(Li e

t al.

2003

) N

use

effi

cien

cy

NU

E=(

Pn f

–Pn c

)÷(S

f f –S

f c)

Sf, s

oil N

ferti

lizer

app

lied

=N

UE

by

(O'H

allo

ran

1998

a)

%

Ferti

lizer

N re

cove

ry c

ompa

red

to z

ero

cont

rol

A

ppar

ent f

ertil

izer

use

N

Uf=

Pn f

–Pn c

Pn

, tot

al p

lant

N c

onte

nt

f, fe

rtiliz

er N

app

licat

ion

c, n

ontre

ated

con

trol o

r low

est N

ap

plic

atio

n do

se

g/g

Doe

s no

t con

side

r am

ount

of f

ertil

izer

app

lied

just

pla

nt N

con

tent

N

har

vest

inde

x N

HI=

Yn÷

Pn

Yn, y

ield

(mar

keta

ble)

N c

onte

nt

%

Th

e pr

opor

tion

of p

lant

N t

hat w

ent t

o yi

eld

(Zeb

arth

et a

l. 20

04a;

Ze

barth

et a

l. 20

04b;

Ze

barth

et a

l. 20

04c)

N u

se e

ffici

ency

N

UE

=Pw

÷Scn

NU

E=N

UpE

×NU

tE

Pw, t

otal

pla

nt d

ry w

eigh

t Sc

n, c

rop

N s

uppl

y =

ferti

lizer

N

appl

ied

+ (fr

om th

e 0

N tr

eatm

ent:

Pn

+ in

orga

nic

soil

N)

g/g

-Bas

ed o

n pl

ant w

eigh

t and

not

pla

nt N

co

nten

t, no

t yie

ld

-Tak

es in

to a

ccou

nt a

ll so

il N

ava

ilabl

e to

cro

p ba

sed

on 0

N tr

eatm

ent

-Ofte

n di

fficu

lt to

est

imat

e S

cn

N

upt

ake

effic

ienc

y N

UpE

=Pn

÷Scn

%

See

abo

ve, b

ut c

onsi

ders

pla

nt N

not

pla

nt

wei

ght

N

util

izat

ion

effic

ienc

y N

UtE

=Pw

÷Pn

g/

g P

ropo

rtion

of p

lant

wei

ght t

hat i

s pl

ant N

Har

vest

inde

x H

I=Y

n÷P

w

%

P

ropo

rtion

of p

lant

wei

ght t

hat i

s yi

eld

N

har

vest

inde

x N

HI=

Yn÷

Pn

%

A

ppar

ent f

ertil

izer

N

reco

very

S

lope

of t

he re

gres

sion

from

a

plot

of P

n by

Sf

-

Take

s in

to a

ccou

nt a

ll N

app

licat

ion

leve

ls

(Joe

rn a

nd V

itosh

19

95b)

N

upt

ake

effic

ienc

y

(w

hole

pla

nt)

NU

pE=P

n÷Sf

%

N

upt

ake

effic

ienc

y

(y

ield

) N

UpE

=Yn÷

Sf

(Err

ebhi

et a

l. 19

99;

Err

ebhi

et a

l. 19

98b)

N

use

effi

cien

cy

NU

E=(

Pn÷

Sf)×

(Pw

÷Pn)

N

UE

=NU

pE×N

UtE

g/

g

N

upt

ake

effic

ienc

y N

UpE

=Pn÷

Sf

%

N

util

izat

ion

effic

ienc

y N

UtE

=(P

w÷P

n)

g/

g

N

reco

very

N

RE

=(P

n f–P

n c)÷

Sf

%

(Err

ebhi

et a

l. 19

99)

Effic

ienc

y of

util

izat

ion

E=(

Pw

)2 ÷(P

n)

g

(E

rreb

hi e

t al.

1998

b)

Effic

ienc

y in

dex

E=(

Pn f

–Pn c

)÷(S

f f –S

f c)

(K

lein

kopf

et a

l. 19

81)

N u

se e

ffici

ency

N

UE

=Pn÷

(Sf+

Sn)

Sn

, tot

al s

oil a

vaila

ble

N

%

Con

side

rs s

oil i

norg

anic

N

(Kel

ling

et a

l. 20

03)

N

UE

=Pn÷

Sf

%

Pag

e 40

of 6

0

Tabl

e 1

Con

tinue

d. D

efin

ition

s an

d m

etho

ds u

sed

to d

eter

min

e ni

troge

n (N

) effi

cien

cy in

dice

s in

diff

eren

t cro

ps.

Ref

eren

ce

Term

C

alcu

latio

n D

efin

ition

U

nits

N

otes

(Z

vom

uya

and

Ros

en

2002

; Zvo

muy

a et

al.

2002

)

N u

se e

ffici

ency

N

UE

=(Y

n f–Y

n c)÷

(Sf f

–Sf c)

N

UE

=NU

pE×N

UtE

Pn

det

erm

ined

afte

r nat

ural

sen

esce

nce

N

upt

ake

effic

ienc

y N

UpE

=(P

n f–P

n c)÷

(Sf f

–Sf c)

%

N h

arve

st in

dex

NH

I=(Y

n f –

Yn c

) ÷ (P

n f–P

n c)

g/

g

H

arve

st in

dex

HI=

Yw

÷Pw

Yw

, yie

ld w

eigh

t

Agr

onom

ic u

se e

ffici

ency

A

UE

=(P

wf–

Pw

c)÷(

Sf f

–Sf c)

g/g

Phy

siol

ogic

al u

se e

ffici

ency

P

UE

=(P

wf–

Pw

c)÷(

Pn f

–Pn c

)

g/g

(T

yler

et a

l. 19

83)

N u

ptak

e ef

ficie

ncy

NU

pE=P

w÷S

f

D

iffer

ence

met

hod

n/a

Isot

ope

met

hod

n/a

Usi

ng 15

N fo

r cal

cula

tion

(Mey

er a

nd M

arcu

m

1998

) C

umul

ativ

e N

use

effi

cien

cy

NU

Ecu

=((Y

n f-Y

n c)÷

Sf))

×10

00

gN

/kg

N

appl

ied

In

crem

enta

l N u

se e

ffici

ency

N

UE

in=(

(Yn f

-Yn f

-1)÷

(Sf n

-Sf n-

1))

×100

0 n-

1 =

the

next

low

est r

ate

gN/k

g N

ap

plie

d C

onsi

ders

NU

E a

s a

func

tion

of

(Vos

199

9)

Effic

ienc

y of

N u

tiliz

atio

n E

NU

=Pn c

÷Sn c

C

alcu

late

d fo

r non

treat

ed

cont

rols

ra

tio

A

ppar

ent f

ertil

izer

N

reco

very

N

RE

=(P

n f–P

n c)÷

(Sf+

Sn)

ratio

Nitr

ogen

use

effi

cien

cy in

dice

s in

CO

LE C

RO

PS

(O'H

allo

ran

1997

, 19

98a,

199

8b)

N u

se e

ffici

ency

N

UE

=(P

n f–P

n c)÷

(Sf f

–Sf c)

%

Con

side

rs in

crea

ses

in p

lant

N d

eriv

ed fr

om

adde

d fe

rtiliz

er N

(B

akke

r 200

5)

N u

se e

ffici

ency

N

UE

=Yw

÷Sf

Yw

exp

ress

ed o

n a

dry

wei

ght

basi

s

(Zeb

arth

et a

l. 19

95)

App

aren

t fer

tiliz

er N

re

cove

ry

Slo

pe o

f the

regr

essi

on fr

om a

pl

ot o

f Pn+

Scn

by

Sf

In a

bove

grou

nd p

lant

plu

s ex

tract

able

soi

l in

orga

nic

N to

75

cm

Acc

ordi

ng to

Boc

k 19

84

Plo

t of P

n by

Sf

Plo

t of Y

n by

Sf

(Z

ebar

th e

t al.

1991

) A

ppar

ent f

ertil

izer

N

reco

very

N

UE

=(Y

n f–Y

n c)÷

(Sf f

–Sf c)

(Boo

ij et

al.

1993

) A

ppar

ent N

reco

very

N

UE

=(P

n f–P

n c)÷

(Sf f

–Sf c)

(Tho

mps

on e

t al.

2000

b; 2

003)

A

ppar

ent N

use

effi

cien

cy

NU

E=(

Pn f

–Pn c

)÷Sf

f

%

Pag

e 41

of 6

0

Tabl

e 1

Con

tinue

d. D

efin

ition

s an

d m

etho

ds u

sed

to d

eter

min

e ni

troge

n (N

) effi

cien

cy in

dice

s in

diff

eren

t cro

ps.

Ref

eren

ce

Term

C

alcu

latio

n D

efin

ition

U

nits

N

otes

(K

riste

nsen

and

Th

orup

-Kris

tens

en

2004

b)

N u

se e

ffici

ency

N

UE

=Pw

÷Sn

Con

side

rs ro

otin

g de

pth

and

othe

r fac

tors

w

hich

influ

ence

N u

ptak

e by

the

plan

t. C

rop

rota

tion

desi

gned

with

NU

E

(Rat

her e

t al.

1999

) N

use

effi

cien

cy

M

ore

plan

t bio

mas

s/yi

eld

for s

ame

N in

put o

r sa

me

plan

t bio

mas

s/yi

eld

for l

ower

N in

put

Nitr

ogen

use

effi

cien

cy in

dice

s in

OTH

ER C

RO

PS

(Gal

lais

and

Hire

l 20

04)

CO

RN

: N

use

effi

cien

cy

NU

E=Y

w÷S

n

N

UE

=NU

pE×N

UtE

NU

E=

NU

tE ×

NU

pE

N

upt

ake

effic

ienc

y N

UpE

=Pn÷

Sn

N u

tiliz

atio

n ef

ficie

ncy

NU

tE=Y

w÷P

n

(Rau

n an

d Jo

hnso

n 19

99)

CE

RE

AL:

N

use

effi

cien

cy

NU

E=(

Yn

– so

il N

+ ra

infa

ll) ÷

Sf

(Goo

d et

al.

2004

) R

EV

IEW

: N

use

effi

cien

cy

NU

E=P

w÷P

n

M

easu

res

C:N

ratio

; doe

sn’t

acco

unt f

or

biom

ass

incr

ease

s

Usa

ge in

dex

UI=

Pw

×(P

w÷P

n)

Acc

ount

s fo

r bio

mas

s in

crea

ses

N

use

effi

cien

cy (y

ield

) N

UE

y=Y

w÷S

n Sn

, soi

l N (f

ertil

izer

app

lied

or

estim

ated

ava

ilabl

e so

il N

)

Ref

lect

s in

crea

sed

yiel

d pe

r uni

t app

lied

N

N

upt

ake

effic

ienc

y N

UpE

=Pn÷

Sn

Mea

sure

effi

cien

cy o

f N u

ptak

e in

to p

lant

N u

tiliz

atio

n ef

ficie

ncy

NU

tE=Y

w÷P

n

Fr

actio

n of

N c

onve

rted

to y

ield

Agr

onom

ic e

ffici

ency

A

E=(

Yw

f–Y

wc)

÷Sf

Mea

sure

s th

e ef

ficie

ncy

of c

onve

rting

app

lied

N to

yie

ld

A

ppar

ent N

reco

very

A

R=(

Pn f

–Pn c

)÷Sf

%

Mea

sure

s th

e ef

ficie

ncy

of c

aptu

ring

N fr

om

soil

P

hysi

olog

ical

effi

cien

cy

PE

=(Y

wf–

Yw

c)÷(

Pn f

–Pn c

)

Ef

ficie

ncy

with

whi

ch c

rops

use

N in

the

plan

t fo

r the

syn

thes

is o

f yie

ld

Pag

e 42

of 6

0

Tabl

e 2.

Sum

mar

y of

site

and

exp

erim

ent c

hara

cter

istic

s of

pot

ato

N fe

rtiliz

er tr

ials

. R

efer

ence

: Lo

catio

n S

oil T

ype

SS

C%

%

O

M

pH

Cul

tivar

Y

ear

Wea

ther

a N

sou

rce

Amou

nt a

pplie

d (k

g N

/ha)

Ti

min

g

Met

hod

Te

chno

logy

(Li e

t al.

2003

) Jo

seph

-R

heau

me

Farm

Lav

al

QC

Gle

yed

hum

o-fe

rric

podz

ol

Tilly

silt

y lo

am

3.9

4.8-

5.1

Sup

erio

r 19

93

1994

19

95

Nor

mal

se

ason

al

rain

fall

NH

4NO

3 0:

0, 7

0:0,

10

5:0,

140:

0,

70:7

0, 1

05:7

0,

140:

70

Pla

ntin

g:

hillin

g S

ide-

dres

sed:

S

ide-

dres

sed

20-y

r sod

-bre

akup

an

d co

ntin

uous

po

tato

rota

tion

(Li e

t al.

1999

) S

t-Cro

ix-d

e-Lo

tbin

iere

, QC

G

leye

d hu

mo-

ferri

c po

dzol

Ti

lly s

ilty

loam

3.

9 6.

3 S

uper

ior

Ken

nebe

c S

now

den

1993

Fa

vora

ble

NH

4NO

3 0:

0, 7

0:0,

10

5:0,

140:

0,

70:7

0, 1

05:7

0,

140:

70

Pla

ntin

g:

hillin

g B

road

cast

: ba

nded

S

od-b

reak

up a

nd

rota

tion

stud

y

19

94

Rel

ativ

ely

wet

N

H4N

O3

19

95

Rel

ativ

ely

dry

NH

4NO

3 :

Ure

a

(Zeb

arth

and

M

ilbur

n 20

03)

Fred

ricto

n N

B

Orth

ic h

umo-

ferri

c po

dzol

s 53

:40:

8 3.

6 6.

3 S

uper

ior

19

99

D

rier t

han

norm

al,

but t

imel

y ra

ins

NH

4NO

3 0:

0, 1

80:0

, 120

:60

Pla

ntin

g:

hillin

g B

ande

d at

pl

antin

g: d

isk

hille

r

n/a

20

00

Nor

mal

m

oist

ure

& te

mp.

(Zeb

arth

et

al. 2

004a

; Ze

barth

et a

l. 20

04b)

Fred

ricto

n N

B

Orth

ic h

umo-

ferri

c po

dzol

s 42

:43:

15

3.5

6.3

Rus

set

Bur

bank

19

99

Drie

r tha

n no

rmal

, bu

t tim

ely

rain

s

NH

4NO

3 0:

0, 4

0:0,

0:8

0,

0:12

0, 0

:160

, 40

:0, 8

0:0,

120

:0,

160:

0, 4

0:12

0,

80:8

0,12

0:40

Pla

ntin

g:

hillin

g B

ande

d at

pl

antin

g: d

isk

hille

r

n/a

42

:40:

18

3.8

6.2

20

00

Nor

mal

m

oist

ure

& te

mp.

0:

0, 4

0:0,

0:8

0,

0:12

0, 0

:160

, 0:

200,

40:

0, 8

0:0,

12

0:0,

160

:0,

200:

0, 4

0:16

0,

80:1

20, 1

20:8

0,

160:

40

53

:32:

15

3.2

6.6

20

01

Dry

late

r in

sea

son

S

ee 2

000

(Zeb

arth

et

al. 2

004c

) Fr

edric

ton

NB

O

rthic

hum

o-fe

rric

podz

ols

53:3

9:8

3.4

6.6

20 d

iffer

ent

varie

ties

1999

D

rier,

hotte

r N

H4N

O3

0, 1

00

Pla

ntin

g B

ande

d

Scr

eeni

ng v

arie

ties

for N

UE

52:4

2:7

3.7

6.0

20

00

Nor

mal

Pag

e 43

of 6

0

Tabl

e 2

Con

tinue

d. S

umm

ary

of s

ite a

nd e

xper

imen

t cha

ract

eris

tics

of p

otat

o N

ferti

lizer

tria

ls.

Ref

eren

ce:

Loca

tion

Soi

l Typ

e S

SC

%

%

OM

pH

C

ultiv

ar

Yea

r W

eath

er a

N s

ourc

e Am

ount

app

lied

(kg

N/h

a)

Tim

ing

M

etho

d

Tech

nolo

gy

(Ars

enau

lt an

d M

alon

e 19

99)

Cha

rlotte

tow

n,

PE

I O

rthic

hum

o-fe

rric

podz

ols

60:2

9:11

2.

3-3.

1 5.

8-6.

1 A

C N

ovac

hip

Nor

Wis

N

orch

ip

1990

W

et M

ay,

Aug

ust,

Sep

t.

n/a

90,1

34,1

79

Pla

ntin

g

Ban

ded

In-r

ow s

paci

ng 2

0.3,

25

.4, 3

0.5

19

91

Wet

A

ugus

t, S

ept.

(Joe

rn a

nd

Vito

sh 1

995a

, 19

95b)

Ent

rican

, MI

Eut

ric

Glo

ssob

roal

fs-

Alfi

c Fr

agio

rthod

s

San

dy

loam

1.

9-1.

7 5.

6-6.

2 R

usse

t B

urba

nk

1988

- 1989

Irrig

ated

aq

ueou

s (N

H4)

2SO

4 0,

56:

0, 1

12:0

, 56

:56,

28

:28:

28:2

8,

56:5

6:56

Pla

ntin

g:

tube

rizat

ion

(TU

):TU

+14

days

: TU

+28

days

Ban

ded:

ba

nded

:TU

+ to

pdre

ssed

an

d irr

igat

ed

E

ast L

ansi

ng

MI

Psa

mm

entic

H

aplu

dalfs

-Ty

pic

Hap

ulda

lfs

San

dy

loam

1.

6 7.

1

1989

(Err

ebhi

et a

l. 19

99)

Bec

ker,

MN

U

dic

Hap

lobo

roll

Loam

y sa

nd

n/a

n/a

Tran

spla

nts

used

Rus

set

Bur

bank

, R

ed N

orla

nd,

Rus

set

Nor

kota

h

1994

19

95

1994

- C

PB

ou

tbre

ak

NH

4NO

3 0,

69:

78:7

8 26

:32:

40

days

afte

r pl

antin

g

Sid

es o

f hill

Scr

eeni

ng S

olan

um

spp.

for N

UE

(Err

ebhi

et a

l. 19

98b)

B

ecke

r, M

N

Udi

c H

aplo

boro

ll Lo

amy

sand

Tr

ansp

lant

s us

ed R

usse

t B

urba

nk,

Red

Nor

land

, R

usse

t N

orko

tah

1993

NH

4NO

3 0,

55:

80:9

0 15

Jun

e,

1 Ju

ly,

19 J

uly

Ban

ded

Scr

eeni

ng

germ

plas

m fo

r NU

E

(Err

ebhi

et a

l. 19

98a)

B

ecke

r, M

N

Udi

c H

aplo

boro

ll Lo

amy

sand

2.

5 6.

7 R

usse

t B

urba

nk

1991

19

92

Irrig

ated

N

H4N

O3

0:0:

0, 0

:135

:135

, 45

:112

:112

, 90

:90:

90,

135:

67:6

7

Pla

ntin

g:

emer

genc

e:

hillin

g

Ban

ded:

si

dedr

esse

d:

side

s of

hills

Spl

it ap

plic

atio

n on

irr

igat

ed p

otat

o

Pag

e 44

of 6

0

Tabl

e 2

Con

tinue

d. S

umm

ary

of s

ite a

nd e

xper

imen

t cha

ract

eris

tics

of p

otat

o N

ferti

lizer

tria

ls.

Ref

eren

ce:

Loca

tion

Soi

l Typ

e S

SC

%

%

OM

pH

C

ultiv

ar

Yea

r W

eath

er a

N s

ourc

e Am

ount

app

lied

(kg

N/h

a)

Tim

ing

M

etho

d

Tech

nolo

gy

(Kle

inko

pf e

t al

. 198

1)

Abe

rdee

n ID

Xe

rolli

c C

alci

orth

ids

Silt

-loam

n/

a n/

a R

usse

t B

urba

nk,

Lem

hi

Rus

set,

Cen

tenn

ial

Rus

set,

Pio

neer

, N

orgo

ld

Rus

set

1977

19

78

1979

Irrig

ated

N

H4N

O3

0, 2

70, 4

05

Pre

plan

t B

road

cast

in

corp

orat

ed

Ear

ly/m

id-s

easo

n vs

la

te s

easo

n cu

ltiva

rs

(Kel

ling

et a

l. 20

03)

Han

cock

, WI

Typi

c ud

ipsa

mm

ents

Lo

amy

sand

R

usse

t B

urba

nk

2000

20

01

n/a

(NH

4)2S

O4

at

emer

genc

e N

H4N

O3

34:0

:0, 3

4:44

:88,

34

:67:

133,

34

:89:

178

Sta

rter:

emer

genc

e :m

id-

tube

rizat

ion

Ban

ded

Non

ioni

c su

rfact

ant

9.34

L ha

-1

(Zvo

muy

a et

al

. 200

2)

Cen

tral M

N

Ent

ic H

aplu

doll

Hub

bard

lo

amy

sand

1.6

6.4

Rus

set

Nor

kota

h 19

97

1998

Irr

igat

ed

NH

4H2P

O4

at p

lant

ing

NH

4NO

3

28:0

:0

28:4

2:42

, 28

:98:

98,

28:1

54:1

54

Sta

rter:

emer

genc

e:hi

lling

Ban

ded

Clo

nal s

elec

tions

(Zvo

muy

a an

d R

osen

20

02)

Cen

tral M

N

Ent

ic H

aplu

doll

Hub

bard

lo

amy

sand

1.6

6.4

New

Leaf

-S

uper

ior,

Sup

erio

r

1997

19

98

Irrig

ated

N

H4H

2PO

4 at

pla

ntin

g N

H4N

O3

28:0

:0

28:4

2:42

, 28

:98:

98,

28:1

54:1

54

Sta

rter:

emer

genc

e:hi

lling

Ban

ded

CP

B re

sist

ant c

lone

(Tyl

er e

t al.

1983

) S

hafft

er, C

A

Was

co

Fine

sa

ndy

loam

n/a

6.9

Whi

te ro

se

1980

n/

a Irr

igat

ed

31.5

cm

(NH

4)2S

O4

0, 6

7, 1

34, 2

02,

270

Pla

ntin

g B

ande

d

n/a

(Mey

er a

nd

Mar

cum

19

98)

Fall

Riv

er

Val

ley,

CA

Ty

pic

Arg

ixer

olls

80

:13:

70

8.4

5.7

Rus

set

burb

ank

1992

1993

Irr

igat

ed

(NH

4)2S

O4

0:56

:112

:168

:224

:44

8 P

lant

ing

B

ande

d D

iffer

ent w

ater

re

gim

es, b

ased

on

ET

19

92

Wet

Jul

y,

Aug

ust,

dry

Sep

t.

(Vos

199

7,

1999

) W

agen

inge

n,

Net

herla

nds

n/a

San

dy

Pro

min

ent

Veb

eca

1989

- 1992

Irrig

ated

C

alci

um

NH

4NO

3 0,

100

, 200

, 300

an

d eq

ual s

plits

at

1, 2

, 3 a

pplic

atio

n tim

es

Pla

ntin

g:1o

r 2

mon

ths

afte

r 50%

em

erge

nce

Bro

adca

st

Spl

it eq

ual a

mou

nts

into

2 o

r thr

ee e

qual

ap

plic

atio

ns

19

93

0:0,

200

:0, 0

:200

, 10

0:10

0,

67:6

7:67

, 250

:50

Pag

e 45

of 6

0

Tabl

e 3.

Sum

mar

y of

nitr

ogen

use

effi

cien

cy in

pot

atoe

s.

Ref

eren

ce

Cul

tivar

O

ptim

al

N ra

te

(kg

N h

a-1)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

due

(kgN

/t yi

eld)

NU

E

Cal

cula

ted

NU

E

Diff

eren

ce in

ap

plie

d an

d cr

op

rem

oval

¥ (k

g N

ha-1

)

Yie

ld im

pact

B

MP

eva

luat

ed

(Li e

t al.

2003

) S

uper

ior

70

40.9

35

.9

22.6

ye

ars

afte

r sod

br

eak-

up

4.6

3.7

6.0

3.9

3.0

4.3

0.8

0.7

1.7

64

56

31

228

154

139

89.5

37

.7

27.2

No

yiel

d be

nefit

or p

enal

ty o

f sp

lit a

pplic

atio

n N

cre

dit o

f 55-

80 k

g N

ha-1

(Li e

t al.

1999

) S

uper

ior

70

19.6

–

32.9

va

ries

with

ro

tatio

n

n/a

n/a

n/a

n/a

n/a

n/a

No

yiel

d be

nefit

or p

enal

ty o

f sp

lit a

pplic

atio

n N

cre

dit o

f 55-

80 k

g N

ha-1

(Zeb

arth

et

al. 2

004a

; Ze

barth

et

al. 2

004b

)

Rus

set

burb

ank

200

20

.6

43.3

di

ffere

nt

year

s

11.1

3.

6 6.

0 2.

4 5.

1 1.

2 45

.2

62

52

-76.

4 -9

6.1

No

yiel

d be

nefit

or p

enal

ty o

f sp

lit a

pplic

atio

n N

o le

achi

ng d

urin

g gr

owin

g se

ason

. S

plit

appl

icat

ion

had

no e

ffect

on

resi

dual

N a

t har

vest

in 2

of 3

yea

rs.

(Zeb

arth

et

al. 2

004c

) E

arly

se

ason

va

rietie

s1 :

100

(0

and

100

on

ly ra

tes

test

ed)

28.9

3.

6 2.

6 1.

0 47

.5

75

-24.

9 Lo

wer

yie

ld o

n 0N

vs

100N

C

ultiv

ar e

arly

var

ietie

s lo

wer

NU

E b

ut

mor

e ye

arly

var

iatio

n in

NU

E th

an

culti

var d

iffer

ence

s

Mid

sea

son

40.0

3.

7 2.

7 1.

0 54

.8

108

8

Late

sea

son

38

.1

4.3

2.4

1.9

57.5

91

8.

6

(Z

ebar

th

and

Milb

urn

2003

)

Sup

erio

r 18

0 49

.0

55.6

di

ffere

nt

year

s

4.20

2.

48

n/a

n/a

n/a

114₤

77

-25.

6 -7

6.6

Spl

it ap

plic

atio

n:

-low

er y

ield

in 1

999,

-n

o yi

eld

adva

ntag

e in

200

0

Var

iabl

e m

iner

al N

in h

ill, in

fluen

ces

soil

sam

plin

g te

chni

que

120:

60

41.4

53

.7

diffe

rent

ye

ars

4.03

2.

92

n/a

n/a

n/a

92₤

87

-54.

9 -6

2.4

assu

me

crop

re

mov

al is

75%

of

crop

upt

ake

(Ars

enau

lt an

d M

alon

e 19

99)

AC

N

ovac

hip

Nor

Wis

N

orch

ip

90

134

134

41.0

48

.6

45.6

n/a

n/a

n/a

n/a

n/a

C

ultiv

ars

resp

ond

diffe

rent

ly to

N

Y

ield

s de

crea

sed

as in

-row

see

dpie

ce

spac

ing

incr

ease

d fro

m 2

5.4

to 3

0.5

cm

Pag

e 46

of 6

0

Tabl

e 3

Con

tinue

d. S

umm

ary

of n

itrog

en u

se e

ffici

ency

in p

otat

oes.

R

efer

ence

C

ultiv

ar

Opt

imal

N

rate

(k

g N

ha-1

)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

due

(kgN

/t yi

eld)

NU

E

Cal

cula

ted

NU

E

Diff

eren

ce in

ap

plie

d an

d cr

op

rem

oval

¥ (k

g N

ha-1

)

Yie

ld im

pact

B

MP

eva

luat

ed

(Joe

rn a

nd

Vito

sh

1995

a,

1995

b)

Rus

set

Bur

bank

, 11

2 (0

and

112

on

ly ra

te

test

ed)

≈35

≈43

diffe

rent

si

tes

6.4

4.7

2.0

3.1

2.9

1.9

3.4

1.8

0.1

34

200

147

77

-5

-10

-30

1 ou

t of 3

exp

erim

ents

had

in

crea

sed

yiel

ds w

ith s

plit

appl

icat

ions

(Err

ebhi

et

al. 1

999)

Tr

ansp

lant

s us

ed

Rus

set

Bur

bank

, R

usse

t N

orko

tah

R

ed N

orla

nd

225

(0 a

nd 2

25

only

rate

s te

sted

)

Yie

ld n

ot

repo

rted

639g

N/

plan

t 43

5 29

8

433

gN/p

lant

39

9 27

0

206

gN/p

lant

36

28

15.5

10

.5

7.5

n/

a

NU

E v

arie

s m

ore

with

yea

r co

mpa

red

to c

ultiv

ar d

iffer

ence

s P

oten

tial t

o us

e So

lanu

m s

pp. t

o in

crea

se N

UE

(Err

ebhi

et

al. 1

998b

) Tr

ansp

lant

s us

ed

Rus

set

Bur

bank

, R

usse

t N

orko

tah

R

ed N

orla

nd

225

(0 a

nd 2

25

only

rate

s te

sted

)

Yie

ld n

ot

repo

rted

304

gN/p

lant

16

1 94

230

gN/p

lant

15

1 89

74

gN/p

lant

10

5

44.8

23

.8

14.3

n/

a R

.Bur

bank

, R.N

orko

tah

=Goo

d N

fora

ger a

nd re

spon

se

Red

Nor

land

=poo

r for

ager

, go

od N

resp

onse

Pot

entia

l to

use

Sola

num

spp

. to

incr

ease

NU

E

(Err

ebhi

et

al. 1

998a

) R

usse

t B

urba

nk

270

(0 a

nd 2

70

only

rate

s te

sted

)

54.4

65

.3

diffe

rent

ye

ars

3.1

3.6

2.2

3.2

0.9

0.4

33.1

56

.1

44

77

-150

.3

-61.

0 N

o di

ffere

nce

in y

ield

but

less

cu

lls w

hen

low

er N

at p

lant

ing

Red

ucin

g %

of N

app

lied

at p

lant

ing

(Kle

inko

pf

et a

l. 19

81)

Rus

set

Bur

bank

, Le

mhi

R

usse

t, C

ente

nnia

l R

usse

t, P

ione

er,

Nor

gold

R

usse

t

270

48.5

5.

1 ≈3

.6±

≈1.5

55

.3

65

-95.

4 N

o re

latio

nshi

p be

twee

n yi

eld

or N

UE

and

dat

e of

mat

urity

. N

o re

latio

nshi

p be

twee

n N

UE

and

da

te o

f mat

urity

.

(Kel

ling

et

al. 2

003)

R

usse

t B

urba

nk

202

46

.0

59.6

di

ffere

nt

year

s

n/a

2.92

2.

76

n/a

66

₤ 81

-6

7.9

-37.

5 N

o be

nefit

of s

urfa

ctan

t on

yiel

d.

In o

ne y

ear,m

ore

crop

N re

mov

al a

t hi

gher

rate

s w

ith s

urfa

ctan

t

Pag

e 47

of 6

0

Tabl

e 3

Con

tinue

d. S

umm

ary

of n

itrog

en u

se e

ffici

ency

in p

otat

oes.

R

efer

ence

C

ultiv

ar

Opt

imal

N

rate

(k

g N

ha-1

)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

due

(kgN

/t yi

eld)

NU

E

Cal

cula

ted

NU

E

Diff

eren

ce in

ap

plie

d an

d cr

op

rem

oval

¥ (k

g N

ha-1

)

Yie

ld im

pact

B

MP

eva

luat

ed

(Zvo

muy

a et

al.

2002

) R

usse

t N

orko

tah

112

224

41.1

42

.2

3.0

3.9

2.7

3.2

0.3

0.7

40.3

36

.6

99

60

-1.0

-8

9.0

Yie

ld in

crea

sed

with

N ra

te in

on

e of

two

year

s.

New

clo

nes

(Zvo

muy

a an

d R

osen

20

02)

New

Leaf

-S

uper

ior,

Sup

erio

r

112

224

8.9

9.2

3.0

2.8

2.2

2.4

0.8

0.4

48.0

47

.9

17

10

-92.

4 -2

01.9

N

o di

ffere

nce

in y

ield

bet

wee

n cl

ones

Tw

o cl

ones

: New

Leaf

, res

ista

nt to

C

PB

, has

hig

her N

UE

at lo

w N

fe

rtiliz

er a

pplic

atio

ns

(Tyl

er e

t al.

1983

) W

hite

rose

13

4 58

.9

n/a

3.0

n/a

64.3

13

2 42

.7

15

N la

bele

d fe

rtiliz

er u

sed

to s

ee N

fro

m fe

rtiliz

er v

s so

il av

aila

ble

N

(Mey

er a

nd

Mar

cum

19

98)

Rus

set

Bur

bank

56

22

4 41

.6

51.6

n/

a 4.

4 3.

2 n/

a >2

00

>300

g

kg-1

327

74

127.

0 -5

8.9

Cal

iforn

ia d

ata

1.1

to 1

.3 E

T c a

pplie

d ov

erhe

ad w

ater

fo

r nea

r max

imum

yie

lds

Aver

age

142

40.7

4.

2 3.

1 1.

3 48

89

-3

6.1

Sta

ndar

d er

ror

13.4

2.

5 0.

4 0.

2 0.

3 4.

8

13.4

Num

ber

18

31

22

23

18

28

27

* In

dica

tes

tota

l pla

nt N

upt

ake

** D

iffer

ent n

umbe

rs in

dica

tes

diffe

renc

es o

bser

ved

in d

iffer

ent y

ears

. H

ighe

st a

nd lo

wes

t num

bers

are

repo

rted.

Cro

p up

take

and

rem

oval

and

oth

er c

olum

n ar

e re

porte

d fo

r eac

h yi

eld.

If

one

N a

pplic

atio

n ra

te is

giv

en, t

hen

valu

es a

re fo

r diff

eren

t cul

tivar

s.

1 Ave

rage

s fo

r ear

ly-,

mid

-, an

d la

te-m

atur

ing

varie

ties

are

repo

rted.

± T

abul

ated

num

bers

bas

ed o

n es

timat

ed v

alue

s ta

ken

from

gra

phs.

¥ P

ositi

ve v

alue

s in

dica

te m

ore

crop

rem

oval

of N

than

ferti

lizer

app

lied

and

vice

ver

sa fo

r neg

ativ

e va

lues

. ₤ N

o N

UE

det

erm

ined

in th

e m

anus

crip

t. V

alue

s ca

lcul

ated

by

NU

pE=P

n÷Sf

×100

or

NU

pE=Y

n÷Sf

×100

dep

endi

ng o

n da

ta a

vaila

ble.

Pag

e 48

of 6

0

Tabl

e 4.

Sum

mar

y of

site

and

exp

erim

ent c

hara

cter

istic

s of

col

e cr

op N

ferti

lizer

tria

ls.

Ref

eren

ce:

Loca

tion

Soi

l Typ

e S

SC

%

OM

%

pH

C

rop:

V

arie

ty

Yea

r W

eath

er

N s

ourc

e Am

ount

app

lied

(kg

N h

a-1)

Tim

ing

M

etho

d

Tech

nolo

gy

(Bak

ker

2005

) S

imco

e, O

N

Bru

niso

lic

Gra

y B

row

n Lu

viso

l

64:3

1:5

1.3

6.6

Bro

ccol

i: D

ecat

hlon

C

apta

in

2000

20

01

Tric

kle

irrig

atio

n 19

7 -2

50

mm

NH

4NO

3 0,

50,

100

, 150

, 20

0, 3

00, 4

00

Tran

spla

ntin

g B

road

cast

in

corp

orat

ed

(McK

eow

n an

d B

akke

r 20

05a,

20

05b)

Sim

coe,

ON

C

aulif

low

er:

Ape

x C

abba

ge:

Hur

on

2003

20

04

Ferti

gate

d n/

a 0

– 40

0

50%

pre

plan

t: 50

% w

eekl

y fe

rtiga

tion

Bro

adca

st:

ferti

gatio

n In

tera

ctio

n of

wat

er a

nd

N

(O'H

allo

ran

1997

) S

imco

e, O

N

2 si

tes:

S

andy

lo

am,

Cla

y lo

am

n/a

n/a

Cab

bage

19

96

Floo

ding

in

Sep

t. N

H4N

O3

100,

270

, 440

Tr

ansp

lant

ing

n/

a In

tera

ctio

n be

twee

n ra

tios

of N

:P:K

(O'H

allo

ran

1998

b)

Sim

coe,

ON

2

site

s:

San

dy

loam

, C

lay

loam

19

97

N

H4N

O3

143,

215

, 286

, 430

Tr

ansp

lant

ing

or

50%

:25%

:25%

pl

antin

g:21

DAT

:49D

AT

n/a

Spl

it ap

plic

atio

ns

(O'H

allo

ran

1998

a)

Sim

coe,

ON

2

site

s:

San

dy

loam

, C

lay

loam

19

98

Dry

N

H4N

O3

100:

0, 2

00:0

, 40

0:0,

50:

25,

50:7

5, 5

0:12

5,

50:1

75, 1

00:2

5,

100:

75, 1

00:1

25,

100:

175

Tran

spla

ntin

g:

21 D

AT

Bro

adca

st o

r st

rip

Spl

it ap

plic

atio

ns a

nd

strip

vs

broa

dcas

t app

ly

(Bél

ec e

t al.

2001

; C

oulo

mbe

et

al. 1

999)

St-C

roix

-de-

Lotb

inie

re,

QC

Bed

ford

S

andy

cl

ay

loam

5.9

B

rocc

oli

1995

19

96

Irrig

ated

C

alci

um

NH

4NO

3 N

min, 5

0 - N

min,

100

- Nm

in, w

ith

four

sid

edre

ss o

f 0,

50,

100

, 150

Tran

spla

ntin

g:

35 D

AT

Bro

adca

st:

side

dres

sed

Pet

iole

sap

test

s to

de

term

ine

suffi

cien

cy

At 3

0 cm

dep

th in

199

6:

Nm

in =

15 1

997:

Nm

in =

33

L’

Aca

die

St-B

lais

e C

lay

loam

6.

5

N

min =

15

(San

ders

on

and

Ivan

y 19

99)

PE

I H

umo-

Ferr

ic

Pod

zols

2.

3 – 3.

3

5.3-

6.1

Bro

ccol

i: P

rem

ium

C

rop

1988

- 1991

n/a

NH

4NO

3 90

:0, 1

20:0

, 150

:0,

78:4

2, 4

8:42

Tr

ansp

lant

ing:

28

DA

T B

road

cast

in

corp

orat

ed

App

licat

ion

met

hod:

br

oadc

ast,

band

ed, s

plit

Loam

y sa

nd –

sa

ndy

loam

B

russ

els

spro

uts:

V

alia

nt

Cab

bage

: Le

nnox

Tran

spla

ntin

g:

48 D

AT

Pag

e 49

of 6

0

Tabl

e 4.

Sum

mar

y of

site

and

exp

erim

ent c

hara

cter

istic

s of

col

e cr

op N

ferti

lizer

tria

ls.

Ref

eren

ce:

Loca

tion

Soi

l Typ

e S

SC

%

OM

%

pH

C

rop:

V

arie

ty

Yea

r W

eath

er

N s

ourc

e Am

ount

app

lied

(kg

N h

a-1)

Tim

ing

M

etho

d

Tech

nolo

gy

(Bow

en e

t al

. 199

9;

Toiv

onen

et

al. 1

994;

Ze

barth

et

al. 1

995)

Aga

ssiz

, BC

E

utric

E

luvi

ated

B

runi

sol

Med

ium

te

xtur

ed

1.9

5.9

Bro

ccol

i: Em

pero

r 19

90

1991

Irr

igat

ed

NH

4NO

3 0:

0, 6

2.5:

62.5

, 12

5:12

5,

187.

5:18

7.5,

31

2.5:

312.

5,

Tran

spla

ntin

g:1

4 D

ATα

B

road

cast

by

han

d n/

a E

qual

spl

its a

nd n

o pr

epla

nt a

pplic

atio

n

(Zeb

arth

et

al. 1

991)

A

gass

iz, B

C

Eut

ric

Elu

viat

ed

Bru

niso

l

Med

ium

te

xtur

ed

5.5

5.5

Cab

bage

: B

arto

lo

1987

Irr

igat

ed

Ure

a

0:0,

50:

50,

100:

100,

120

:120

20

0:20

0, 2

50:2

50

Pre

-tran

spla

nt:

early

Jun

e B

road

cast

in

corp

orat

ed:b

road

cast

4.0

5.7

19

88

(Kow

alen

ko

and

Hal

l 19

87a,

19

87b)

Aga

ssiz

, BC

E

utric

E

luvi

ated

B

runi

sol

Med

ium

te

xtur

ed

n/a

n/a

Bro

ccol

i: P

rem

ium

C

rop

1979

Nor

mal

ea

rly,

then

dry

NH

4NO

3 25

, 125

, 250

P

lant

ing,

dire

ct

seed

ed

Bro

adca

st

inco

rpor

ated

n/

a E

valu

ated

N ra

te

impa

ct o

n m

atur

ity

19

82

Dry

-Jun

, w

et-J

ul

NH

4NO

3 0,

25,

125

, 250

(Let

ey e

t al.

1983

) S

anta

Ana

C

A

Tupi

c Xe

roflu

vent

S

andy

lo

am

n/a

n/a

Bro

ccol

i: G

reen

C

omet

1980

D

ry la

nd

+ Irrig

ated

NH

4 Fe

rtiga

tion:

N

H4N

O3

30:3

0:30

, 60

:60:

60, 9

0:90

:90

Ferti

gatio

n- 3

0:

with

all

irrig

atio

n ev

ents

for 4

2 D

AT

Pla

ntin

g:15

D

ATα

:35D

AT

Ferti

gatio

n-

plan

ting:

irrig

ati

on w

ater

Ban

ded

Ferti

gatio

n –

dow

n fu

rrow

s

Ferti

gatio

n vs

soi

l ap

plie

d

S

orre

nto

CA

C

alci

c H

aplo

xero

ll Lo

am

19

81

Dry

land

+ Irr

igat

ed

NH

4 Fe

rtiga

tion:

U

AN

38:3

8:38

, 75:

75:7

5 P

lant

ing:

42

DA

Pα :5

6DA

P Fe

rtiga

tion-

pl

antin

g:irr

igat

ion

wat

er

(Tho

mps

on

et a

l. 20

00a,

20

00b)

Ariz

ona

Tupi

c N

atia

rgid

S

andy

lo

am

2.9

8.5

Cau

liflo

wer

: C

andi

d C

harm

Win

ter

1993

D

rip

Ferti

gate

dFe

rtiga

tion

UA

N

60, 3

40, 4

50, 6

00

5 fe

rtiga

tion

appl

icat

ions

S

ub-s

urfa

ce

ferti

gatio

n N

rate

by

wat

er

inte

ract

ions

W

inte

r 19

9419

95

100,

200

, 300

, 500

Pag

e 50

of 6

0

Tabl

e 4.

Sum

mar

y of

site

and

exp

erim

ent c

hara

cter

istic

s of

col

e cr

op N

ferti

lizer

tria

ls.

Ref

eren

ce:

Loca

tion

Soi

l Typ

e S

SC

%

OM

%

pH

C

rop:

V

arie

ty

Yea

r W

eath

er

N s

ourc

e Am

ount

app

lied

(kg

N h

a-1)

Tim

ing

M

etho

d

Tech

nolo

gy

(Tho

mps

on

et a

l. 20

02a,

20

02b)

Ariz

ona

Tupi

c N

atia

rgid

S

andy

lo

am

2.9

8.5

Bro

ccol

i: C

laud

ia

Win

ter

1993

D

rip

Ferti

gate

dFe

rtiga

tion

UA

N

60, 4

40, 3

50, 5

00

5 fe

rtiga

tion

appl

icat

ions

S

ub-s

urfa

ce

ferti

gatio

n N

rate

by

wat

er

inte

ract

ions

W

inte

r 19

9419

95

100,

200

, 300

, 500

(Tho

mps

on

et a

l. 20

03)

Ariz

ona

Tupi

c N

atia

rgid

S

andy

lo

am

Bro

ccol

i: M

arat

hon

Win

ter

1998

D

rip

Ferti

gate

dFe

rtiga

tion

UA

N

200,

300

4

ferti

gatio

n sc

hedu

les

Sub

-sur

face

fe

rtiga

tion

N ra

te b

y w

ater

in

tera

ctio

ns

W

inte

r 19

9920

00

250,

300

(Van

Den

B

ooga

ard

and

Thor

up-

Kris

tens

en

1997

)

Den

mar

k

San

dy

loam

C

aulif

low

er:

Pla

na o

r S

iria

1993

19

94

Irrig

ated

C

alci

um

NH

4NO

3 A

ccor

ding

to N

su

pply

; 170

-400

P

lant

ing:

bas

ed

on m

ax. r

oot

grow

th

n/a

(Sor

ense

n 19

99)

Den

mar

k

San

dy

loam

C

abba

ge

Cal

cium

N

H4N

O3

0, 6

0, 1

20, 2

40,

480,

960

n/

a

Dire

ct s

eede

d

Bro

ccol

i

N

H4N

O3

20, 1

15, 2

10, 4

00

trans

plan

ted

(Lis

iew

ska

and

Km

ieci

k 19

96)

Pol

and

Lo

amy-

silty

B

rocc

oli:

Cor

vet F

1 C

aulif

low

er:

Ser

nio

RS

NH

4NO

3 40

:40,

40:

40:4

0 Tr

ansp

lant

ing:

21

DA

T:35

D

AT

n/a:

sid

e dr

ess

Food

qua

lity

para

met

ers

asse

ssed

: NO

3-N

, NO

2-N

, vita

min

C

(Rat

her e

t al

. 199

9)

Ger

man

y N

ethe

rland

s

Lo

amy-

silt

clay

Cau

liflo

wer

F 1

: Mar

ine

Lind

uria

n Li

nfor

d

1993

19

94

C

alci

um

NH

4NO

3 N

min, 2

50 b

ased

on

Nm

in

Tran

spla

ntin

g

n/a

Scr

eeni

ng c

ultiv

ars

Bar

e ro

ot tr

ansp

lant

s

α DA

T, d

ays

afte

r tra

nspl

antin

g; D

AP

, day

s af

ter p

lant

ing.

Pag

e 51

of 6

0

Tabl

e 5.

Sum

mar

y of

nitr

ogen

use

effi

cien

cy in

col

e cr

ops.

R

efer

ence

C

rop:

V

arie

ty

Opt

imal

N

rate

(k

g N

ha-1

)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

dueψ

(k

gN/t

yiel

d)

Cal

cula

ted

NU

E

Diff

eren

ce

in

appl

ied

and

crop

re

mov

al¥

(kg

N h

a-1)

Diff

eren

ce

in a

pplie

d an

d cr

op

upta

ke¥

(kg

N h

a-1)

Yie

ld re

spon

se to

N ra

te

(kg

N h

a-1)

BM

P e

valu

ated

BR

OC

CO

LI

(B

akke

r 200

5)

Bro

ccol

i: D

ecat

hlon

31

5 17

.2

22.4

5.

8 16

.6

31.4

-2

16.2

69

.0

ME

RN

=297

-312

(Bél

ec e

t al.

2001

; C

oulo

mbe

et a

l. 19

99)

Bro

ccol

i 25

0 hi

ghes

t ra

te te

sted

≈19

≈11.

5

diffe

rent

ye

ars

Line

ar re

spon

se to

N s

ugge

sts

high

er y

ield

s w

ith h

ighe

r N

rate

s

(San

ders

on a

nd

Ivan

y 19

99)

Bro

ccol

i: P

rem

ium

C

rop

150

high

est

rate

test

ed

9.3

5.9

N in

le

aves

15

0 br

oadc

ast h

ighe

st y

ield

co

mpa

red

to 1

20 o

r 90

band

ed

or s

plit

Yie

ld: s

plit

> ba

nded

br

oadc

ast =

spl

it br

oadc

ast =

ban

ded

(B

owen

et a

l. 19

99; T

oivo

nen

et

al. 1

994;

Zeb

arth

et

al.

1995

)

Bro

ccol

i: Em

pero

r 12

5 25

0 25

0 di

ffere

nt

plan

ting

date

s

18.0

13

.9

17.4

15.3

20

.8

22.6

4.3

5.9

7.6

11.0

14

.9

15.0

62.2

32

.8

52.8

-47

-168

-1

18

144

40

143

Incr

ease

N =

cur

vilin

ear

incr

ease

in y

ield

= c

urvi

linea

r in

crea

se in

N u

ptak

e =

decr

ease

NU

E

Opt

imum

rate

for 3

to 4

hea

d bu

nche

s w

eigh

ing

tota

l of 6

80 g

244

300

302

diffe

rent

pl

antin

g da

tes

19.5

14

.5

18.0

15.9

21

.7

23.3

4.6

6.1

7.8

11.2

15

.6

15.5

37.0

29

.5

46.4

-153

-2

11

-162

65

16

116

395∞

, 508

, 410

In

crea

se N

= c

urvi

linea

r in

crea

se in

yie

ld =

cur

vilin

ear

incr

ease

in N

upt

ake

= de

crea

se N

UE

No

com

paris

ons

of 1

:1 s

plit

appl

icat

ion

poss

ible

to p

repl

ant

appl

icat

ion

Env

ironm

enta

l opt

imum

-<10

0 of

re

sidu

al N

39

5∞

508

410

diffe

rent

pl

antin

g da

tes

20.4

15

.9

18.6

16.6

23

.2

24.3

5.0

6.9

8.3

11.6

16

.3

16.1

25.7

₤ 21

.6

37.4

-293

-3

98

-256

-56.

7 -1

38

42.5

244,

300

, 302

max

imum

N

ferti

lizer

rate

s gi

ves

0.5-

1 to

nne

ha-1

redu

ctio

n in

yie

ld

Incr

ease

N =

cur

vilin

ear

incr

ease

in y

ield

= c

urvi

linea

r in

crea

se in

N u

ptak

e =

decr

ease

NU

E

No

com

paris

ons

of 1

:1 S

plit

appl

icat

ion

poss

ible

to p

repl

ant

appl

icat

ion

ME

RN

Val

ues

Pag

e 52

of 6

0

Tabl

e 5

Con

tinue

d. S

umm

ary

of n

itrog

en u

se e

ffici

ency

in c

ole

crop

s.

Ref

eren

ce

Cro

p:

Var

iety

O

ptim

al

N ra

te

(kg

N h

a-1)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

dueψ

(k

gN/t

yiel

d)

Cal

cula

ted

NU

E

Diff

eren

ce

in

appl

ied

and

crop

re

mov

al¥

(kg

N h

a-1)

Diff

eren

ce

in a

pplie

d an

d cr

op

upta

ke¥

(kg

N h

a-1)

Yie

ld re

spon

se to

N ra

te

(kg

N h

a-1)

BM

P e

valu

ated

436

558

441

diffe

rent

pl

antin

g da

tes

20.4

16

.0

18.6

16.8

23

.2

24.6

5.1

7.1

8.4

11.7

16

.1

16.2

23.8

20

.2

35.4

-332

-4

45

-285

-93.

9 -1

87

17

244,

300

, 302

max

imum

N

ferti

lizer

rate

s gi

ves

0.5-

1 to

nne

ha-1

redu

ctio

n in

yie

ld

Incr

ease

N =

cur

vilin

ear

incr

ease

in y

ield

= c

urvi

linea

r in

crea

se in

N u

ptak

e =

decr

ease

NU

E

No

com

paris

ons

of 1

:1 s

plit

appl

icat

ion

poss

ible

to p

repl

ant

appl

icat

ion

Max

imum

yie

ld v

alue

s

(Kow

alen

ko a

nd

Hal

l 198

7a, 1

987b

) B

rocc

oli:

Pre

miu

m

Cro

p

250

high

est

rate

test

ed

11.7

16

.6

diffe

rent

ye

ars

10.1

10

.2

8.1

6.0

2.0

4.2

38.0

₤ 39

.6

-155

-1

51

-89

19

Hig

hest

rate

= 2

50 =

hig

hest

yi

eld

Effe

ct o

f N ra

te o

n m

atur

ity

(Let

ey e

t al.

1983

) B

rocc

oli:

Gre

en

Com

et

270

high

est

rate

test

ed

8.8

4.1

76.0

₤

-100

H

ighe

st ra

te =

270

= h

ighe

st

yiel

d B

ette

r fer

tiliz

er re

cove

ry o

f soi

l ap

plie

d vs

ferti

gatio

n

225

high

est

rate

test

ed

17.4

13

.4

7.2

6.2

55.6

₤ -1

00

9 H

ighe

st ra

te =

225

= h

ighe

st

yiel

d

(Tho

mps

on e

t al.

2002

a, 2

002b

) B

rocc

oli:

Cla

udia

35

0 13

.0

18.9

11

.5

diffe

rent

ye

ars

23.5

12

.7

24.8

n/a

87

.4₤

69.0

81

.3

-4

4 -1

08

-66

Cap

ture

s 95

% o

f max

. yie

ld fo

r al

l 3 y

ears

(n

ear)

opt

imal

agr

onom

ic,

econ

omic

, and

env

ironm

enta

l ou

tcom

es

410

436

390

di

ffere

nt

year

s

13.3

19

.6

11.6

25.5

14

25

.3

82.7

₤ 63

.1

75.4

-7

1 -1

61

-96

Cal

cula

ted

N ra

tes

to g

ive

max

imum

yie

lds

Tabl

e 5

Con

tinue

d. S

umm

ary

of n

itrog

en u

se e

ffici

ency

in c

ole

crop

s.

Ref

eren

ce

Cro

p:

Var

iety

O

ptim

al

N ra

te

(kg

N h

a-1)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

dueψ

(k

gN/t

yiel

d)

Cal

cula

ted

NU

E

Diff

eren

ce

in

appl

ied

and

crop

Diff

eren

ce

in a

pplie

d an

d cr

op

upta

ke¥

Yie

ld re

spon

se to

N ra

te

(kg

N h

a-1)

BM

P e

valu

ated

Pag

e 53

of 6

0

rem

oval

¥ (k

g N

ha-1

) (k

g N

ha-1

)

(Tho

mps

on e

t al.

2003

) B

rocc

oli:

Mar

atho

n 35

0 21

.1

13.9

5.

7 8.

2 34

.6₤

70.6

§ -2

29

-56

No

diffe

renc

e in

ferti

gatio

n fre

quen

cy o

n yi

eld

Low

N: h

ighe

r NU

E w

ith b

i-w

eekl

y fe

rtiga

tion.

Hig

h N

: no

diffe

renc

e (S

oren

sen

1999

) B

rocc

oli

400

16

4.9

19.6

-321

Li

near

(Lis

iew

ska

and

Kmie

cik

1996

) B

rocc

oli:

Cor

vet F

1 12

0 hi

ghes

t ra

te te

sted

23.2

79

.6 α

N

O3-

N

Hig

her y

ield

with

hig

her N

rate

. M

ore

NO

3-N

and

NO

2-N

with

hi

gher

N ra

te

Mor

e V

itam

in C

in c

aulif

low

er

with

hig

her N

Av

erag

e se

28

2 15

.4

15.4

6.

5 9.

1 37

.7

-203

-7

8 S

tand

ard

erro

r 26

1.

3 2.

5 0.

3 2.

2 7.

7 36

46

B

rocc

oliΩ

Num

ber

15

12

7 5

6 6

5 7

CAB

BAG

E (M

cKeo

wn

and

Bak

ker 2

005a

) C

abba

ge:

Hur

on

400

20

0 10

0 ≈3

5 4.

2 8.

2 2.

4 3.

5 1.

7 3.

5 60

.2₤

61.5

-1

59

-77

15

86

Hig

hest

yie

ld a

t 100

% fi

eld

capa

city

& h

igh

N

(O'H

allo

ran

1997

) C

abba

ge

440

60

.2

4.7µ

2.3

2.4

31.8

₤ -3

00

-160

H

ighe

st ra

te 4

40 =

hig

hest

yi

eld,

Nm

ax =

382

ME

RN

=

363

Littl

e ev

iden

ce o

f im

porta

nce

of

N:P

:K ra

tios

(O'H

allo

ran

1998

b)

Cab

bage

M

ER

N s

plit

=318

M

ER

N p

repl

ant =

234

H

igh

prep

lant

rate

s –r

educ

tion

in

yiel

d

ME

RN

spl

it =3

89

ME

RN

pre

plan

t = 4

06

(O'H

allo

ran

1998

a)

Cab

bage

34

9 88

.0

Pre

trans

plan

t N

max

= 3

59

ME

RN

=349

(San

ders

on a

nd

Ivan

y 19

99)

Cab

bage

: Le

nnox

15

0 hi

ghes

t ra

te te

sted

58.8

4.

18

N in

le

aves

15

0 br

oadc

ast h

ighe

st y

ield

co

mpa

red

to 1

20 o

r 90

band

ed

or s

plit

Yie

ld: b

road

cast

= s

plit

> ba

nded

(Zeb

arth

et a

l. 19

91)

Cab

bage

: B

arto

lo

635

609

calc

ulat

ed

diffe

rent

ye

ars

100

129

2.

7 1.

9

42.9

₤ 39

.6

-362

-3

68

ME

RN

= 6

30 a

nd 6

07 k

g N

ha-1

.

(Sor

ense

n 19

99)

Cab

bage

≈4

00

76

2.2

46.7

-189

Q

uadr

atic

pla

teau

Aver

age

273

70.3

3.

7 2.

4 2.

8 46

-2

30

-111

S

tand

ard

erro

r 32

.4

6.3

0.8

0.1

0.7

8.2

79

64

Cab

bage

Ω

Num

ber

12

10

3 2

3 3

2 3

Tabl

e 5.

Sum

mar

y of

nitr

ogen

use

effi

cien

cy in

col

e cr

ops.

Pag

e 54

of 6

0

Ref

eren

ce

Cro

p:

Var

iety

O

ptim

al

N ra

te

(kg

N h

a-1)

Yie

ld *

* (t

ha-1

) C

rop

N

upta

ke

(kgN

/t

yiel

d)

Cro

p N

re

mov

al

(kgN

/t

yiel

d)

Pla

nt

resi

dueψ

(k

gN/t

yiel

d)

Cal

cula

ted

NU

E

Diff

eren

ce

in

appl

ied

and

crop

re

mov

al¥

(kg

N h

a-1)

Diff

eren

ce

in a

pplie

d an

d cr

op

upta

ke¥

(kg

N h

a-1)

Yie

ld re

spon

se to

N ra

te

(kg

N h

a-1)

BM

P e

valu

ated

CAU

LIFL

OW

ER

(McK

eow

n an

d B

akke

r 200

5b)

Cau

liflo

wer

: A

pex

400ℓ

20

0 27

23

9.

4 9.

8 3.

5 3.

9 5.

9 5.

9 23

.5₤

45.0

-3

06

-110

-1

46

26

2004

–m

axim

um #

1 cu

rds

yiel

d of

21

t ha-1

at N

rate

of

292

Irrig

atio

n di

d no

t affe

ct y

ield

(Tho

mps

on e

t al.

2000

a, 2

000b

) C

aulif

low

er:

Can

did

Cha

rm

450

27.8

8.

9 2.

6 6.

3 16

.3

50.7

§ -3

77

-210

C

aptu

res

95%

of m

ax. y

ield

for

all 3

yea

rs.

350-

400

N ra

tes

prov

ided

(nea

r) op

timal

agr

onom

ic, e

cono

mic

, an

d en

viro

nmen

tal o

utco

mes

(V

an D

en

Boo

gaar

d an

d Th

orup

-Kris

tens

en

1997

)

Cau

liflo

wer

: P

lana

or

Siri

a

250

N s

uppl

y 20

.1

23.8

di

ffere

nt

year

s

9.2

9.2

3.0

2.9

6.2

6.3

24.4

₤ 27

.6

-189

-1

81

-65

-30

No

yiel

d or

qua

lity

resp

onse

to

N

Mea

sure

d re

sidu

al N

67

and

51 a

t har

vest

N s

uppl

y of

250

is s

uffic

ient

and

m

inim

izes

env

ironm

enta

l ris

k

(Lis

iew

ska

and

Kmie

cik

1996

) C

aulif

low

er:

Ser

nio

RS

12

0 hi

ghes

t ra

te te

sted

31

13

0.5α

N

O3-

N

Hig

her y

ield

with

hig

her N

rate

. M

ore

NO

3-N

and

NO

2-N

with

hi

gher

N ra

te

(Rat

her e

t al.

1999

) C

aulif

low

er

F 1: M

arin

e 25

0

N s

uppl

y 85

∩

40

3.2%

-4.

2% N

in

leav

es

N s

uppl

y of

250

is s

uffic

ient

be

caus

e le

af N

con

tent

was

be

twee

n 3.

2-4.

2%

Aver

age

243

26.4

9.

2 3.

0 6.

2 21

.9

-289

-1

34

Sta

ndar

d er

ror

28.2

6.

0 0.

1 0.

1 0.

02

4.0

78

66

`Cau

liflo

wer

Ω

Num

ber

13

12

3 4

3 3

3 3

BR

USS

ELS

SPRO

UTS

(San

ders

on a

nd

Ivan

y 19

99)

Bru

ssel

sp

rout

s:

Val

iant

150

high

est

rate

test

ed

11.1

3.

92

N in

le

aves

15

0 br

oadc

ast h

ighe

st y

ield

co

mpa

red

to 1

20 o

r 90

band

ed

or s

plit

No

yiel

d di

ffere

nce

with

ap

plic

atio

n m

etho

d

Aver

age

147

17.2

S

tand

ard

erro

r 31

.8

6.2

Bru

ssel

s sp

rout

s Ω

Num

ber

3 2

¥ Pos

itive

val

ues

indi

cate

mor

e cr

op re

mov

al (o

r upt

ake)

of N

than

ferti

lizer

app

lied

and

vice

ver

sa fo

r neg

ativ

e va

lues

. ∞ M

ER

N v

alue

s us

ed to

det

erm

ine

optim

al N

rate

. B

rocc

oli:

ferti

lizer

cos

t $0.

75 a

nd c

rop

$0.3

8 kg

-1.

Cab

bage

: fer

tiliz

er c

ost $

0.9

and

crop

$0.

13 k

g-1.

₤ N

o N

UE

pre

sent

ed in

the

man

uscr

ipt.

Val

ues

calc

ulat

ed b

y N

UpE

=Yn÷

Sf×1

00 o

r whe

re th

at d

ata

was

not

ava

ilabl

e N

UpE

=Pn÷

Sf×1

00 w

as u

sed,

whe

re Y

n, a

nd P

n is

N c

onte

nt in

tota

l pla

nt a

nd

yiel

d po

rtion

, res

pect

ivel

y an

d Sf

equ

als

soil

N fe

rtiliz

er a

pplie

d.

µ E

stim

ated

bas

ed o

n lit

erat

ure

whe

re c

rop

N u

ptak

e is

typi

cally

1.5

-2 ti

mes

hea

d N

upt

ake.

ψ

Est

imat

ed b

ased

on

the

diffe

renc

e of

cro

p N

upt

ake

and

crop

N re

mov

al.

Pag

e 55

of 6

0

∩ Y

ield

resu

lt in

man

uscr

ipt e

xpre

ssed

as

dry

wei

ght.

Val

ues

repo

rted

are

base

d on

an

assu

med

10%

dry

wei

ght f

or c

aulif

low

er.

ℓ Yie

ld p

rese

nted

as

No.

1 g

rade

cur

ds, t

otal

yie

ld n

ot p

rovi

ded.

§ A

ppar

ent N

UE

cal

cula

ted

in th

e m

anus

crip

t as

NU

E=(

Pn f

–Pn c

)÷Sf

f α H

ead

N c

onte

nt n

ot re

porte

d. V

alue

s ar

e kg

NO

3-N

ha-1

. Ω C

alcu

latio

ns: a

vera

ge, s

tand

ard

erro

r, an

d nu

mbe

r are

bas

ed o

n da

ta p

rese

nted

in T

able

s 5

and

6.

Pag

e 56

of 6

0

Tabl

e 6.

Col

e cr

op re

spon

se to

N fe

rtiliz

atio

n.

CR

OP

: Ref

eren

ce

Loca

tion

Var

iety

N

rate

s te

sted

(k

g N

ha-1

) O

ptim

al N

rate

(k

g N

ha-1

) Y

ield

(to

nne

ha-1

) Y

ield

resp

onse

to N

rate

BR

OC

CO

LI

B

RO

CC

OLI

(M

cKeo

wn

and

Bak

ker 2

003)

S

imco

e, O

N

25

0 or

300

n/a

Onl

y on

e ra

te te

sted

(Duf

ault

and

Wat

ers

1985

) M

inne

sota

S

outh

ern

Com

et

56, 1

12, 1

68, 2

24

224

10.1

Li

near

£

(Kah

n et

al.

1991

) O

klah

oma

Pre

miu

m C

rop

37, 7

4, 1

12, 1

49

149

8.0

Line

ar£

No

yiel

d re

spon

se in

3 o

f 4

year

s (li

kely

rate

s w

ere

too

low

, up

to 2

80 k

g N

ha-1

) (B

urne

tte e

t al.

1993

) Te

nnes

see

13

4, 2

69, 4

03

403

n/a

n/a

(Gut

ezei

t 200

4)

Ger

man

y Em

pero

r 30

0 34

0- 4

00¥

32

4 g/

head

17

48 g

/ to

tal p

lant

Box

plo

t stu

dies

: 4.

7% a

nd

4.6%

N c

onte

nt in

hea

d an

d re

sidu

e.

CAB

BAG

E

CAB

BAG

E

(M

cKeo

wn

and

Bak

ker 2

003)

S

imco

e, O

N

Hur

on

250

or 3

00

88

O

nly

one

rate

test

ed

(Wes

terv

eld

et a

l. 20

04)

Sim

coe,

ON

A

tlant

is

0, 8

5, 1

70, 2

55,

340

85-3

40

69.6

N

o yi

eld

diffe

renc

e be

twee

n 85

-340

N

o re

spon

se in

oth

er y

ear.

(W

arne

r et a

l. 20

04)

Har

row

, ON

C

hine

se

Cab

bage

0,

100

, 200

, 300

or

0, 6

0, 1

10,

160,

210

210

or 3

00

3.54

kg

/hea

d Li

near

£

(Hec

kman

et a

l. 20

02)

New

Jer

sey,

D

elaw

are,

C

onne

ctic

ut

New

Yor

k

Aut

umn

Cab

bage

0

45, 9

0, 1

35,

180,

225

If

NO

3-N

>30

th

en 0

N n

eede

d =

10-1

6

135N

; =

1-9

180

N

≈75

Line

ar re

spon

se to

soi

l NO

3-N

at

14

-21

DAT

(Bur

nette

et a

l. 19

93)

Tenn

esse

e

134,

269

, 403

40

3 n/

a n/

a (W

iede

nfel

d 19

86)

Texa

s S

anni

bel

84, 1

68, 2

52 o

r 11

2, 1

68, 2

69

252

or 2

69

29.2

Li

near

resp

onse

to N

(Wel

ch e

t al.

1985

a)

Cal

iforn

ia

0,

50,

100

, 150

, 20

0 10

0 sp

lit o

r 15

0 pr

epla

nt

60.0

58

.6

No

diffe

renc

e in

yie

ld b

etw

een

split

and

pre

plan

t at 1

50 k

g N

ha

-1. H

ighe

r yie

ld w

ith 1

00 k

g N

ha-1

split

vs.

pre

plan

t.

Pag

e 57

of 6

0

Tabl

e 6

Con

tinue

d. C

ole

crop

resp

onse

to N

ferti

lizat

ion.

C

RO

P: R

efer

ence

Lo

catio

n V

arie

ty

N ra

tes

test

ed

(kg

N h

a-1)

Opt

imal

N ra

te

(kg

N h

a-1)

Yie

ld

(tonn

e ha

-1)

Yie

ld re

spon

se to

N ra

te

(Roz

ek e

t al.

1999

; S

ady

et a

l. 19

98)

Pol

and

Erm

a F 1

18

0

8.9

Onl

y on

e ra

te te

sted

(Kol

ota

et a

l. 19

92)

Pol

and

Kam

ienn

a G

low

a 20

0

68.1

-40.

6 R

ecom

men

ded

rate

(Kris

tens

en a

nd

Thor

up-K

riste

nsen

20

04b)

Den

mar

k

100

12

.3 p

lant

bi

omas

s no

t yie

ld

Onl

y on

e ra

te te

sted

. N

de

ficie

ncy

obse

rved

.

(Eve

raar

ts a

nd B

ooij

2000

) N

ethe

rland

s B

ently

B

ased

on

Nm

inℓ

0, N

, 2xN

, 3xN

, 4x

N, 5

xN, 2

N+N

330

– 1.

5Nm

in

Rel

ativ

e (%

) yie

ld

repo

rted

No

N c

yclin

g di

ffere

nce

band

ing

and

broa

dcas

t, or

pr

epla

nt a

nd s

plit

appl

icat

ion

(Fel

ler a

nd F

ink

1999

) G

erm

any

20

0¥

n/a

Est

imat

e pl

ant N

upt

ake

as

394-

416

and

224

for c

abba

ge

and

kohl

rabi

, res

pect

ivel

y (G

upta

and

Sam

notra

20

04)

Indi

a G

olde

n A

cre

0, 3

0, 6

0, 9

0, 1

20

76.8

36

.3

Qua

drat

ic

(Cha

o et

al.

2004

) C

hina

C

hine

se

Cab

bage

17

4

49.3

-40.

7 O

nly

one

rate

test

ed

CAU

LIFL

OW

ER

C

AULI

FLO

WER

(D

ufau

lt an

d W

ater

s 19

85)

Min

neso

ta

Sno

w C

row

n 56

, 112

, 224

11

2-22

4 11

.7

No

yiel

d at

56,

no

diffe

renc

e be

twee

n tw

o hi

ghes

t rat

es

(Ros

en 1

990)

M

inne

sota

S

now

Cro

wn

Sel

f Bla

nche

Im

peria

l 10-

6

67, 1

34, 2

01

201

18.2

Li

near

£ N

o im

pact

on

tipbu

rn in

cide

nce

(Wel

ch e

t al.

1985

a)

Cal

iforn

ia

0,

70,

140

, 210

, 28

0 14

0 21

.8

Spl

it ap

plic

atio

ns y

ield

hig

her

than

pre

plan

t (W

elch

et a

l. 19

87;

Wel

ch e

t al.

1985

b)

Cal

iforn

ia

0,

30:

30, 6

0:60

, 90

:90,

120

:120

90

:90

17.9

N

o di

ffere

nce

in y

ield

s at

90:

90

and

120:

120

kg N

ha-1

. (B

atal

et a

l. 19

97)

Geo

rgia

W

hite

Em

pres

s S

tove

pipe

10

1, 2

13, 2

69 o

r 15

7, 2

13, 3

81

269

or 3

81

9.9

12.9

D

iffer

ence

s in

cul

tivar

re

spon

se to

N. L

inea

r£ -Whi

te

Empr

ess:

qua

drat

ic -S

tove

pipe

(E

vera

arts

and

De

Moe

l 199

5)

Net

herla

nds

Frem

ont

Pla

na

Bas

ed o

n N

min

0, N

, 2xN

, 3xN

, 4x

N, 2

N+N

224

– N

min

Rel

ativ

e (%

) yie

ld

repo

rted

No

yiel

d di

ffere

nce

band

ing

and

broa

dcas

t, or

pre

plan

t and

sp

lit a

pplic

atio

n (K

ulde

ep e

t al.

2004

) In

dia

Sno

wba

ll,

RC

-Job

-1

120,

150,

180

180

31.7

Li

near

£

Pag

e 58

of 6

0

Tabl

e 6

Con

tinue

d. C

ole

crop

resp

onse

to N

ferti

lizat

ion.

C

RO

P: R

efer

ence

Lo

catio

n V

arie

ty

N ra

tes

test

ed

(kg

N h

a-1)

Opt

imal

N ra

te

(kg

N h

a-1)

Yie

ld

(tonn

e ha

-1)

Yie

ld re

spon

se to

N ra

te

BR

USS

ELS

SPRO

UTS

BR

USS

ELS

SPRO

UTS

(W

elch

et a

l. 19

85a)

C

alifo

rnia

0, 4

5, 9

0, 1

35,

180

90

23.4

Y

ield

s w

ere

no d

iffer

ent f

or

high

er N

rate

s co

mpa

red

to 9

0 kg

N h

a-1.

(Boo

ij et

al.

1993

) N

ethe

rland

s K

undr

y 0,

100

, 200

, 300

20

0

Yie

ld n

ot

repo

rted

∞

Com

pila

tion

of tr

ials

whe

re n

itrog

en u

se e

ffici

ency

was

not

eva

luat

ed o

r cou

ld n

ot b

e ca

lcul

ated

. £ L

inea

r res

pons

e su

gges

ts h

ighe

r yie

lds

at h

ighe

r N ra

tes

¥ Bas

ed o

n fe

rtiliz

er N

and

soi

l min

eral

N a

t pla

ntin

g.

ℓ Nm

in is

soi

l min

eral

N a

t pre

plan

t N a

pplic

atio

n.

Page 59 of 60

Table 7. Recommended N fertilization rates for potatoes grown in different provinces or states. Location N rate

(lb/ac) Timing Criteria

Ontario 45 67 116 178 62 53

At planting 15 t ha-1 expected marketable yield 60 25 30+ mineral early crop muck early and main crop

Nova Scotia New Brunswick PEI

50 75-100

Preplant, incorporate Banded at planting

Loams & silt loams

Nova Scotia New Brunswick PEI

50 100

Banded at planting Sidedress at 1st cultivation

Quebec 125 Loam soil Manitoba 0-170 Split applications Dry land –soil nitrate-N and yield goal 0-260 Irrigated –soil nitrate-N and yield goal Michigan 150-210 1/3 at planting,

1/3 at hilling 1/3 with irrigation

Yield goal

Ohio 100-150 2/3 at planting 1/3 sidedress 4-5” tall

Mineral soil –clay

Ohio 170-180 2/3 at planting 1/3 sidedress 4-5” tall

–sand

New York 75-100 0-100

At planting At sidedress 4-8” tall

Reduce by 75 lbs for good stand alfalfa or clover

Pennsylvania 50 75-100

Preplant incorporate Banded at planting

Loams & silt soils

Pennsylvania 50 100

Preplant incorporate Sidedress 4 to 5 wks

Sandy loams

Wisconsin 30-200 Based on yield goal and organic matter

Minnesota 0-250 Based on previous crop, organic matter and yield goal

Illinois & Indiana 24-30 50-60 50-60

At planting At emergence At hilling

Page 60 of 60

Table 8. Recommended N fertilization rates for cole crops grown in different provinces or states. Location N rate

(lb/ac) Timing Crop and Criteria

Ontario 89 27

Preplant incorporate Sidedress 3 wks

Broccoli, cauliflower, Brussels sprouts -mineral soil -extra 36 N if excessive rains on sand

Ontario 116 36

Preplant incorporate Sidedress 3 wks

Cabbage -mineral soil -extra 36 N if excessive rains on sand

Nova Scotia New Brunswick PEI

50-100 50 50

Preplant incorporate Sidedress 2 -3 wks Sidedress 4 – 6 wks

Broccoli & cauliflower

Nova Scotia New Brunswick PEI

50-75 25-50

Preplant incorporate Sidedress 4 – 5 wks

Brussels sprouts

Nova Scotia New Brunswick PEI

50-75 25-50 25-50

Preplant incorporate Sidedress 2 -3 wks Sidedress if needed

Cabbage

Quebec 135 85 at transplanting 50 4 - 5 weeks

Loam soil

Manitoba 55-90 Split applications Unless a soil test is used Michigan 60

30-40 30-40

Preplant incorporate at transplanting at 4 wks except cabbage

Ohio 75-150 30-60 30-60

Preplant incorporate at 4-5 leaves at head formation

New York 40 40 20-40

Preplant incorporate Banded at planting Sidedress at 4 wks.

Pennsylvania 50-100 50 50

Preplant incorporate Sidedress 2-3 wks Sidedress 4-6 wks

Broccoli

Pennsylvania 50-75 25-50 25-50

Preplant incorporate Sidedress 2-3 wks If needed later

Cabbage, cauliflower & Brussels sprouts

Illinois & Indiana 80-120 60

Preplant incorporate Sidedress 2-3 wks

Higher rate for soils les than 3% organic matter

Wisconsin 25-100 40-80 40-120

split split split

Broccoli & Brussels sprouts OM 0-2% Cabbage OM. = 20-2% Cauliflower OM. = 20-2%

Minnesota 100-180 1/3 preplant incorporate 1/3 at 2 wks. 1/3 at 5 wks.

Higher rate for soils low in organic matter

Kansas 45 30-35

Preplant incorporate at 3-5 wks

Kentucky 50 50 50

Preplant incorporate when head begins forming 2 wks later

Colorado 40 40 20-40

Preplant incorporate banded at planting sidedress 4 wks.