Soil & Tillage Research 144 (2014) 141–149

Amelioration of soil acidity and soybean yield after surface limereapplication to a long-term no-till integrated crop-livestock systemunder varying grazing intensities

Amanda Posselt Martins a,*, Ibanor Anghinoni a, Sérgio Ely V.G.de Andrade Costa a,Filipe Selau Carlos a, Gabriela de Holanda Nichel a, Rodrigo André Pereira Silva a,Paulo César de Faccio Carvalho b

aDepartment of Soil Science, Federal University of Rio Grande do Sul, PO Box 15100, Porto Alegre, RS 91540-000, BrazilbDepartment of Forage Plants and Agrometeorology, Federal University of Rio Grande do Sul, Porto Alegre, RS,Brazil

A R T I C L E I N F O

Article history:Received 4 December 2013Received in revised form 1 May 2014Accepted 29 July 2014

Keywords:pHBase saturationAluminum saturationLimingIntegrated systems

A B S T R A C T

An integrated crop-livestock system (ICLS), with summer grain cropping and winter grazing of covercrops, is an option for agricultural management in subtropical areas. Despite numerous studiesevaluating ICLS, there have been limited investigations of soil acidity and lime application dynamics insuch systems. Because grain producers resist introducing livestock into cultivation areas due to fear ofnegative impacts of grazing on soybean yields and lime movement thorough the soil profile, the objectiveof this research is to evaluate the impacts of surface lime reapplication on the amelioration of soil acidityattributes and the yield of soybean in a long-term integrated soybean-beef cattle system under no-tillunder varying grazing intensities. An experiment was established in 2001 for an ICLS on a RhodicHapludox soil. Crop succession consisted of soybean (Glycine max) cultivation during summer and a mixof black-oat (Avena strigosa) + Italian ryegrass (Lolium multiflorum) during winter. Treatments consisted ofvarying grazing intensities during winter: intensive grazing, moderate grazing, and no-grazing. Lime wasapplied to the surface of the entire area at the beginning of the experiment, and a reapplication wasperformed nine years later (May of 2010) in a sub-parcel scheme (with and without lime reapplication).Soil acidity attributes (pH, base saturation and aluminum saturation) were evaluated at 12, 18, 24, and30 months after lime reapplication, and the soybean yields of the 2010/11, 2011/12, and 2012/13 seasonswere measured. As previously observed for the first surface lime application performed in the same trialarea, the present study demonstrated that ICLS, regardless of grazing intensity, did not inhibit soilimprovement in deeper layers after surface lime reapplication. In fact, the presence of animals helps toameliorate soil acidity in deeper layers, compared to non-grazed areas. The soybean yield was notcorrelated with the soil acidity attributes and was affected by lime reapplication only under intensivegrazing and drought conditions. However, when summer rainfall was lower than the expectedclimatological normal, soybean yields were higher in non-grazed areas.

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1. Introduction

Surface lime (re)application remains a controversial topicregarding food production system management. The efficiency ofthis agronomic practice to correct soil acidity in the soil profile underno-tillage (NT) systems has been widely studied because thereacidification process can result in a greater increase in soil acidityin deeper soil layers compared to the upper layers (Tang and Rengel,

* Corresponding author. Tel.: +55 51 3308 7420.E-mail address: amandaposselt@gmail.com (A.P. Martins).

http://dx.doi.org/10.1016/j.still.2014.07.0190167-1987/ã 2014 Elsevier B.V. All rights reserved.

2003). Varying results of the effects of surface liming on the soilprofile have been observed,with limingaffectingsoil layersto depthsofonly5 cm(Rheinheimeretal., 2000;Amaraletal., 2004a)aswellassoil layers of 40 cm or deeper (Oliveira and Pavan, 1996; Caires et al.,2008). According to Edmeades and Ridley, (2003) such differencesexist because, in addition to the effects of the liming rate and time,several other factors affect this dynamic, such as: rainfall distribu-tion, soil texture, structure (presence of macro and biopores),hydraulic conductivity, fauna (which mix soil layers), crop rotationand management, and residue additions, among others.

Additionally, the yield responses of crops to surface liming arenot clear because the degree of impact depends on all the

142 A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149

previously mentioned factors in addition to crop tolerance toacidity. In contrast to conventional tillage, under NTconditions, soilacidity attributes do not have a direct relationship with the cropresponses to lime application, especially under normal rainfallconditions (Caires et al., 2001; Tissi et al., 2004). Furthermore,Brown et al. (2008) have reported that, in long-term NT systems,there is little or no crop response to liming because thedecomposition of residues accumulated in the soil surface resultsin pH buffering and aluminum complexation.

Despite the latter, there is not a great deal of research that hasexamined the acidity and lime application dynamics of integratedcrop-livestock systems (ICLS). In regions with acidic soils, most ofthe ICLS experiments only consider liming as a necessaryagronomical practice for increasing crop and meat production.However, animal grazing in cropping areas modifies the fluxes andprocesses affecting the soil-plant-atmosphere continuum, impos-ing heterogeneity in the spatial distributions of nutrients impactedby selective grazing and residue (dung and urine) deposition(Anghinoni et al., 2013; Moraes et al., 2013). Thus, the dynamicsassociated with grazed conditions may influence the responses ofsoils and crops to surface liming compared to the responses of NTsystems that are only used for the cultivation of cash and covercrops (non-grazed systems). However, the grazing intensity is acritical factor that influences the modifications that will occur inthe system, including those related to soil chemical attributes(Carvalho et al., 2011).

When well managed, grazing stimulates root growth (Lyons andHanselka, 2001), which can increase the volume of rhizosphericsoil and organic ligand exudation (Curl and Truelove, 1986), thusincreasing aluminum complexation and the mobility of limedissolution byproducts (Ca2+ and Mg2+ ) through the soil profile.Such processes are enhanced by the deposition of cattle dung(amount and distribution) (Haynes and Mokolobate, 2001; Liu andHue, 1996), which depends on grazing intensity (Silva et al., 2014).In addition, decomposition of roots contributes to higher macro-porosity and pore continuity along the soil profile (biopores)(Stirzaker et al., 1996), improving the translocation of fine limeparticles from upper to deeper soil layers, thus increasing the soilpH in deeper layers (Amaral et al., 2004b). On the other hand, theimpacts of cattle trampling under intensive grazing result inphysical damage, increasing soil bulk density and decreasing soilmacroporosity, hydraulic conductivity and infiltration rates(Bell et al., 2011). Such modifications of the soil system can slowthe redistribution of lime through the soil profile. Furthermore,acidification, caused by urination (Black, 1992) and nitrogenfertilizer additions in grazed systems (Unkovich et al., 1998),inhibits the impacts of liming in deeper soil layers. Such potentialnegative impacts of grazing on soil improvement by surface limingand summer crop yields contribute to the ongoing resistance ofgrain producers to adopting ICLS.

In a previous study conducted in the same trial area, Flores et al.(2008) verified that ICLS conditions, compared to non-grazedsystems, increased the liming efficiency in deeper soil layers overtime. Higher values of soil pH and base saturation and lower levelsof aluminum saturation were observed at 24 months after limingup to 20 cm deep in grazed areas; for non-grazed areas, the benefitsof liming only reached a depth of 15 cm. However, in this study,there was not long-term effects of varying grazing intensities onsoil physical attributes because surface liming was performedduring the trial establishment. Furthermore, the response of thegrain crop to liming was not evaluated because the area (despitetreatments) was broadcast limed. Thus, the objective of the presentstudy is to evaluate the impacts of surface lime reapplication onthe amelioration of acidity attributes over the soil profile and theresponse of soybean yield in a long-term no-till integrated crop-livestock system under varying grazing intensities.

2. Materials and methods

This research was conducted as part of an experimentestablished at the Espinilho Farm (Agropecuaria Cerro Coroado)located in the Planalto region of the state of Rio Grande do Sul(Brazil) (28�5702300S latitude and 54�2102200W longitude). Theexperimental area, approximately 22 ha, is located at an altitude of465 m in the Brazilian subtropics, with a warm humid summer(Cfa) climate according to the Köeppen classification system. Themean annual temperature is 19 �C and the mean annualprecipitation is 1850 mm (data from the INMET, 2013). The areapresents a declivity of 0.02–0.10 m m�1. The soil is a deep,well-drained and dark-red clayey Oxisol (Rhodic Hapludox–SoilSurvey Staff, 1999) (540, 270 and 190 g kg�1 of clay, silt and sand,respectively).

Prior to the establishment of the experiment, the area had beencultivated under NT since 1993. In November of 2000, the soil wassampled and analyzed for the chemical characterization of the 0–5,5–10, 10–15 and 15–20 cm layers. Soil organic matter, pH, availableP and K (Mehlich 1), exchangeable Ca, Mg and Al; and base andaluminum saturation values ranged from: 42 to 26 g kg�1; 4.9 to4.6; 13.4 to 3.7 mg kg�1; 240 to 55 mg kg�1; 62 to 40 mmolc kg�1;22 to 11 mmolc kg�1; 7 to 1 mmolc kg�1; 48 to 34% and 17 to 4%. Theexperiment started, after soil sampling, with soybean cultivation,followed by a black oat+Italian ryegrass mixed-pasture grazingseason. Then, the cropping rotation has been conducted under anICLS, with summer soybean cultivation from November until Mayand winter black oat+Italian ryegrass grazing from May untilNovember.

Each year, pasture establishment occurs with black oat seeding(45 kg ha�1) and Italian ryegrass natural reseeding. Neutered malesteers aged approximately 12 months are moved into the area inthe first half of July (when the forage accumulation has,approximately, reached a dry matter production of 1500 kg ha�1

and a 20 cm sward height) when they weigh approximately 200 kg,simulating a cattle fattening or finishing system. During thegrazing season, cattle feeding was forage-based. Treatmentsconsisted of varying grazing intensities during winter, determinedby the grazing sward heights. The grazing sward heights were10 cm (intensive grazing-IG) and 20 cm (moderate grazing-MG), aswell as a non-grazed (NG) treatment, organized in a randomizedblock design with three replicates. A continuous grazing systemwas adopted (with a minimum of three remaining steers=testers).Sward heights were measured every 14 days by the Sward stickmethod (Bircham, 1981), which consists of a graduated-stickmeasurement system, with a “marker” that slides up and down todetermine the height of the first forage leaf blade. In each plot, thesward heights of approximately 100 randomized readings (points)were recorded. The mean sward height is affected by the grazingintensity (stocking rates) and adding or removing steers from eachplot. In the three years considered for this study, the mean stockingrates of cattle liveweight (LW) during the grazing seasons for theintensive and moderate grazing treatments, respectively, were1182 and 917 kg LW ha�1 in 2010, 902 and 752 kg LW ha�1 in 2011,and 911 and 816 kg LW ha�1 in 2012.

Pasture desiccation, achieved with glyphosate (900 g a.i. ha�1)and ethylic chlorimuron (37.5 g a.i. ha�1) was performed after eachgrazing season, and in December of each year, soybean was seededat a density of 45 seeds m�1 with a 45 cm row spacing. Seedinoculation followed the technical recommendations (specificproduct). Agronomic management was conducted according totechnical recommendations (use of herbicides, insecticides,fungicides) and the soybean crop was harvested every May. Anon-acidity-tolerant soybean cultivar (Nidera RR) was cropped inthe three growing seasons evaluated in this study (2010/11,2011/12 and 2012/13).

A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149 143

2.1. Liming and fertilization

Broadcast liming, with a total neutralization relative power(TNRP) of 62%, at a rate of 4.5 Mg ha�1, was performed between thefirst grazing and soybean seasons (November 2001). Effects ofliming were observed for 48 months. Thereafter, the effects ofliming decreased and the soil returned to pre-established acidicconditions (unpublished data). Thus, in May of 2010, soil wascollected and analyzed for background conditions (Table 1) andthen broadcast lime was reapplied in sub-plots (20 � 30 m) withinall the plots at a rate of 3.6 Mg ha�1 (TNRP of 74%). Thisexperimental design resulted in plots with and without limereapplication. The calculated liming rates, according to Chemistryand Soil Fertility Commission of the Rio Grande do Sul and SantaCatarina States (CQFS RS/SC, 2004), aimed to elevate the soilpH–H2O to 5.5 in the 0 to 10 cm soil layer.

All treatments received the same level of soil fertilization,consisting of N applications (as urea) during the pasture seasonand phosphorus (as triple superphosphate) and potassium(as potassium chloride) fertilizations prior to the soybean seasonto, based upon soil analysis, achieve a 4.0 to 7.0 Mg ha�1 forage drymatter yield and a 4.0 Mg ha�1 soybean yield, according to CQFSRS/SC (2004). Thus, the base fertilization for soybean consisted of300 kg ha�1 of 0–20–30 before the 2006/07 season (except for5–20–20 in 2002/03) and 300 kg ha�1 of 0–20–20 from 2007/08 to2012/13 seasons. The nitrogen application rates for pasturefertilization were 45 kg ha�1 in 2001, 2002, 2004, 2005, 2006,2007, 2008, and 2010; 90 kg ha�1 in 2003, 2009, and 2011; and140 kg ha�1 in 2012. From the winter of 2012 onwards, fertilizermanagement was changed to a “system” based management, withnutrient additions for both soybean and pasture applied onlyduring the winter. Thus, soybean base fertilization was performedat pasture seeding. When the N application rates were greater than45 kg ha�1, two applications, at 30 and 60 days after forageestablishment, were performed.

2.2. Soil sampling and analysis

Soil samples were collected up to a depth of 40 cm at 12, 18, 24,and 30 months after lime reapplication (May of 2010). The first andthird soil samplings were performed at the end of the 2010/11 and2011/12 soybean seasons (May). The second and fourth samplingswere performed at the end of 2011 and 2012 grazing seasons(November). Samples were stratified into 12 layers: 0–2.5, 2.5–5,5–7.5, 7.5–10, 10–12.5, 12.5–15, 15–17.5, 17.5–20, 20–25, 25–30,30–35 and 35–40 cm. Soils were sampled from three representa-tive sites within each subplot (lime reapplication) inside thegrazing treatments. For the 0–20 cm layer, shovel sampling wasconducted, and a Dutch auger was used for the 20–40 cm layer.Samples were transported, in plastic bags, to the Soil Fertility

Table 1Acidity attributes of the soil profile immediately prior to surface lime reapplication(May 2010) to the long-term no-till integrated crop-livestock system (soybean-beefcattle) experiment evaluating varying grazing intensities. IG: intensive grazing(10 cm pasture sward height); MG: moderate grazing (20 cm pasture sward height);NG: no grazing.

Layer,cm

pH-H2O Base saturation, % Al saturation, %

IG MG NG IG MG NG IG MG NG

0 to 5 4.9 4.9 5.1 71 68 60 4 4 135 to 10 4.8 4.8 4.8 62 61 44 9 9 3110 to 15 4.7 4.7 4.6 51 54 37 18 19 4115 to 20 4.6 4.6 4.6 44 40 27 29 32 5320 to 30 4.5 4.5 4.5 28 27 24 49 47 5930 to 40 4.4 4.5 4.4 22 21 17 55 54 66

Research Laboratory of the Federal University of Rio Grande do Sul(UFRGS), dried, crushed (2 mm mesh) and stored in plastic pots.

The following analyses were performed on the soil samples:pH–H2O (1:1 ratio) and SMP index (to estimate potential acidityH + Al); exchangeable Ca, Mg and Al (1 M KCl); and availableK (Mehlich-1), according to Tedesco et al. (1995). These dataallowed for the calculation of base saturation, as a percentage,([K+ + Ca2+ + Mg2+]/CECpH 7.0; with CECpH 7.0 defined as the sum ofK+, Ca2+, Mg2+ and H + Al) and aluminum saturation, as apercentage, (Al3+/effective CEC; with effective CEC defined asthe sum of K+, Ca2+, Mg2+ and Al3+). The soil pH–H2O, basesaturation and aluminum saturation, according to CQFS RS/SC(2004), were considered as soil acidity indicators for this study. Theresults were expressed as the difference between areas that didand did not receive lime reapplication (D).

2.3. Soybean yield

Soybean yields were determined for the 2010/11, 2011/12 and2012/13 cropping seasons, corresponding to the periods from 6 to12, 18 to 24, and 30 to 36 months after lime reapplication. Harvestswere performed by hand at the time of crop maturation bysampling plants in a 4.5 m2 area (five random sites inside eachsubplot). At the UFRGS Soil Department, samples were threshed,cleaned and weighed using an analytical balance. Grain moisturewas determined and adjusted to 130 g kg�1.

2.4. Rainfall

The climate normal and precipitation (rainfall) data for thesoybean and grazing seasons evaluated (Fig. 1) were obtained fromthe three nearest meteorological stations: Cruz Alta, Santa Mariaand Sao Luiz Gonzaga counties (INMET, 2013).

2.5. Statistical analysis

Results were submitted to analysis of variance (ANOVA) and,when significant (p < 0.05), means were compared by Tukey test(p < 0.05). The following statistical models were used for ANOVA:

a) Change in soil acidity attributes of the soil profile:

Yijkl = m + Bi + Sj + Error a (ij) + Gk + SjGk + Error b (ijk) + Ll + Error c(il) + SjLl + GkLl + SjGkLl + Error d (ijkl)where m: overall experimentmean; B: blocks (i = 1, 2, 3); S: sampling time (j = 1, 2, 3, 4) G:grazing intensity (k = 1, 2, 3); L: soil layer (l = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,11, 12); and Error = experimental error.

b) Soybean yield:

Yijk = m + Bi + Gj + Error a (ij) + Rk + Error b (ik) + GjRk + Error c (ijk)where m: overall experiment mean; B: blocks (i = 1, 2, 3); G: grazingintensity (k = 1, 2, 3); R: lime reapplication (j = 1, 2); and Error:experimental error.

3. Results

3.1. Change in pH

Regarding changes in pH (DpH), the three-way ANOVA wassignificant (p < 0.05) and the results are graphed by sampling time(12, 18, 24 and 30 months after lime reapplication), comparing(Tukey test, p < 0.05) treatments for each depth and depths foreach treatment. However, all interactions among the sources ofvariation (sampling time, grazing intensity, and depth) wereexamined and used to describe and discuss the results.

Fig. 1. Accumulated precipitation for the soybean (a) and grazing (b) seasons of a long-term no-till integrated crop-livestock system (soybean-beef cattle) and climatologicalnormal of the experiment location. Soybean season: November–March. Grazing season: June–November.

144 A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149

The amelioration of soil acidity by liming, evaluated by pHvalues, reached 17.5, 20 and 7.5 cm at 18, 30 and 18 months afterlime reapplication for the IG, MG and NG treatments, respectively.An increase in the pH of the superficial layer (0–5 cm) of all thetreatments was verified 12 months after lime reapplication(Fig. 2a) (May 2011, end of 2010/11 soybean season), and theimpacts of liming under NG were greater than under IG and MG inthe 2.5–5 cm layer (Fig. 2a). Six months later (Fig. 2b) (18 months

Fig. 2. Change in soil pH–H2O (with and without re-liming) at 12 (a), 18 (b), 24 (c) and 30livestock system (soybean-beef cattle) under varying grazing intensities. Lime was reappthe experiment (2001). Bars (—) represent the least significant difference (LSD) by Tuk

after lime reapplication, November 2011, end of 2011 grazingseason), NG also presented higher DpH values in the 0–2.5 cmlayer. Below this depth, under NG conditions, the DpH decreased,as observed for MG. However, in the subsurface layers (betweenthe 7.5 and 15 cm depths), IG resulted in a higher DpH from surfaceliming.

Twenty-four months after lime reapplication (Fig. 2c) (May2012, end of 2011/12 soybean season), under IG, higher DpH values

months (d), after surface lime reapplication to a long-term no-till integrated crop-lied in May 2010. The entire area was surface broadcast with lime in the beginning ofey test (p < 0.05).

A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149 145

occurred to a depth of 15 cm. However, 30 months after limereapplication (Fig. 2d) (November 2012, end of 2012 grazingseason) a shift in behavior was detected. All the treatmentspresented similar (p > 0.05) DpH values to a depth of 7.5 cm, whilechanges in pH (DpH> � 0) were observed to depths of 10 and 7.5 cmfor IG and NG, respectively. For MG, such changes in pH reached the20 cm depth, with greater DpH values in the 7.5–20 cm layercompared to the NG and IG treatments.

3.2. Change in base saturation

For changes in base saturation (DV) (Fig. 3), only significanttwo-way interactions were observed in the ANOVA (p > 0.05),between: (1) sampling time and depth, for the means amonggrazing intensities (Fig. 3a); and (2) grazing intensity and depth, forthe means among sampling times (Fig. 3b). Despite suchobservations, the greatest changes in base saturation(DV> 10–15%) occurred in the upper 7.5 cm (Fig. 3).

Considering sampling time (Fig. 3a), the DV was lower across theentire soil profile at 12 months after lime reapplication. In the top7.5 cm depth, the highest DV values were observed at 30 monthsafter lime reapplication. However, below the 12.5 cm depth, thehighest DV values were observed at 18 months after limereapplication, which were similar to the DV at 30 months afterlime reapplication in some soil layers (Fig. 3a). Thus, the highest DVvalues always occurred after the pasture (winter) season, highlight-ing the impacts of soybean cropping on soil acidity (Bolan et al.,1991). However, such amelioration of acidity is temporary becausethe decomposition of organic (plant) residues results in increasedsoil acidity (Butterly et al., 2013). Such dynamics can characterize asoil’s “chemical-resilience” and buffering capacity, by alternatinghigher and lower soil acidity conditions.

The patterns DV among sampling times, grazing intensities anddepths were evaluated (Fig. 3b). In the soil surface (up to 7.5 cm),the IG and NG treatments resulted in higher (p < 0.05) DV values(by between 15 and 25%) compared to MG. For subsurface layers(10–40 cm), the lowest and highest DV values were observed underthe NG and MG conditions, respectively. The MG and IG treatmentsresulted in similar DV values in only the 10–20-cm soil layer(Fig. 3b).

Fig. 3. Change in soil base saturation (with and without re-liming) at 12,18, 24 and 30 momeans of all sampling times under intensive, moderate and no grazing (b), for a long-termin May 2010. The entire area was surface broadcast with lime in the beginning of the expe(p < 0.05).

3.3. Change in aluminum saturation

Changes in aluminum saturation (Dm) (Fig. 4) according to thethree-way ANOVA (p > 0.05) and graphics followed the samepattern and design as for DpH (Fig. 2). For the discussion ofaluminum saturation, higher Dm values were considered as morenegative Dm values. Significant (p < 0.05) impact on Dm due tore-liming were detected to a depth of 40 cm under grazingconditions (IG or MG), with the highest changes observed at18 months after lime reapplication. On the other hand, impacts onDm values only reached a depth of 17.5 cm under NG at 24 monthsafter lime reapplication. The discrepancies among the Dm values at12, 18, 24 and 30 months after lime reapplication (Fig. 4a–d) alsoindicate seasonality in soil acidity under the ICLS conditions(soybean and grazing cycles), as observed for base saturation(Fig. 3a).

Twelve months after lime reapplication (Fig. 4a), changes inaluminum saturation (Dm> � 0) were only observed in the surfacelayer (up to 7.5 cm), as observed for DpH (Fig. 2a) and DV (Fig. 3a).In the NG treatment, higher Dm values were observed to a 5 cmdepth. For the 5–7.5 cm layer, the IG treatment was associated withlower aluminum saturation (higher Dm) in limed areas (Fig. 4 a). At18 months after lime reapplication (Fig. 4b), the treatments weresimilar (p > 0.05) for the 7.5 cm soil layer. However, for the7.5–10 cm layer, NG and MG presented higher Dm values. Onthe other hand, IG was more efficient in decreasing aluminumsaturation from the 7.5–17.5 cm soil layer, and similar to MG from17.5–25 cm. Below this depth, MG presented the highest Dm valuesto the depth of 40 cm (Fig. 4b).

At 24 months after lime reapplication, the changes inaluminum saturation (Dm 3 0) in the NG treatment to a depthof 17.5 cm were notable, with lower values for IG and MG (Fig. 4c).However, after the second grazing season evaluated (30 monthsafter lime reapplication), MG presented higher Dm to a depth of40 cm, while NG only affected aluminum saturation in the surfacelayers (2.5–7.5 cm) (Fig. 4d). The higher amelioration of soilacidity under grazed conditions obtained at 18 and 30 monthsafter lime reapplication (end of pasture season), especially forbase and aluminum saturation (Figs. 3b,c and 4b,c), highlight the

nths after surface lime reapplication: the means of all the grazing treatments (a), the no-till integrated crop-livestock system (soybean-beef cattle). Lime was reapplied

riment (2001). Bars (—) represent the least significant difference (LSD) by Tukey test

Fig. 4. Change in soil aluminum saturation (with and without re-liming) at 12 (a), 18 (b), 24 (c), and 30 months (d), after surface lime reapplication for a long-term no-tillintegrated crop-livestock system (soybean-beef cattle) under varying grazing intensities. Lime was reapplied in May 2010. The entire area was surface broadcast with lime inthe beginning of the experiment (2001). Bars (—) represent the least significant difference (LSD) by Tukey test (p < 0.05).

146 A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149

impacts of grazing on the efficiency of surface liming across thesoil profile.

3.4. Maximum soil correction

Fig.s with higher absolute values obtained in each soil layer overthe 30 months after lime reapplication were evaluated (formaximum soil correction) by inspection, without statisticalanalysis, to categorize the acidity attributes across the soil profileinto 4 groups: “very low” (VL), “low” (L), “medium” (M) and “high”(H), according to the CQFS RS/SC (2004) (Fig. 5). The thresholdvalues considered by the CQFS RS/SC (2004) for adequate plantgrowth are those between the L and M classes. Overall, all thetreatments achieved such values in the upper 10 cm soil. The CQFSRS/SC (2004) considers the 0–10 cm soil layer for liming raterecommendations under long-term NT conditions. Thus, such aresult was expected and the actual liming rate recommendation forthe study region was not able to increase the values of the soilbelow the 20 cm depth above the VL classification for pH and basesaturation (Fig. 5a,b) or the H classification for aluminumsaturation (Fig. 5c).

3.5. Soybean yield

Despite the effect of lime reapplication (p < 0.05) on soil acidityattributes under different grazing intensities (Figs. 2, 3 and 4),liming only affected soybean yield in one (2011/12) of the three

evaluated cropping seasons (Table 4). For the first soybean seasonafter lime reapplication (2010/11, 6–12 months after liming), nodifferences were observed among the treatments and the averageyield was 3.27 Mg ha�1 (Table 4). This result was not unexpectedbecause the impacts of liming were small during the first12 months after lime reapplication (Figs. 2a, 3a and 4a).

A severe drought (less than 50% of the expected rainfall byclimatological normal) (Fig.1a) affected the second soybean seasonafter lime reapplication (2011/12, 18–24 months after). Thus,soybean yields were much lower than expected. However, theseconditions of water-stress resulted in different grazing intensityimpacts on the soybean response (p < 0.05) to lime reapplication.For IG, areas that received lime reapplication in May 2010 pre-sented higher yields, whereas no liming impacts on soybean yieldwere observed under the MG and NG conditions (Table 4). Between18 and 24 months after lime reapplication (corresponding to the2011/12 soybean season), IG was associated with the highestchanges in pH, base and aluminum saturation caused by surfaceliming (Figs. 2b, 3b, and 4b,c) and was the treatment with thehighest DpH across the soil profile at these sampling times. Theseimpacts most likely contributed to the higher yields under IG forthe limed areas during the 2011/12 soybean season (Table 4).

In the third and last soybean season evaluated (2012/13,30–36 months after lime reapplication), no differences in surfaceliming effects were observed among treatments. In contrast,differences (p < 0.05) in soybean yield among grazing intensities,regardless of lime reapplication, were observed. Grazed treatments

Fig. 5. Maximum soil correction for each depth measured for pH (a), base saturation (b) and aluminum saturation (c), for a long-term no-till integrated crop-livestock system(soybean-beef cattle) under varying grazing intensities. VL: very low; L: low; M: medium; H: high; according to CQFS RS/SC (2004). Lime was reapplied in May 2010. Theentire area was surface broadcast with lime in the beginning of the experiment (2001).

A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149 147

(IG or MG) had lower yields compared to NG. The first “system”-based fertilization, with soybean P and K fertilizations applied atpasture seeding and a higher N rate application occurred in thewinter preceding the 2012/13 soybean season. The higher N rateapplied resulted from high soil C:N ratio stocks, as observed byAssmann et al. (2014), and the low forage N content (unpublisheddata). This modification most likely increased the pasture growthrate, resulting in a high cattle stocking rate (911 and 816 kgLW ha�1, for IG and MG, respectively). Cattle trampling may havecaused negative soil physical impacts, such as decreases in soilmacroporosity and increases in soil strength, leading to low wateravailability under conditions of water-stress (Fig. 1), a majorlimiting abiotic factor of cash crop yields.

3.6. Relationship between soybean yield and soil acidity attributes

In general, the soybean yield during the three cropping seasonsevaluated after the lime reapplication did not respond to liming(Table 4). This finding may be, in part, explained by the absence of arelationship between the relative soybean yield and any attributeof soil acidity in the 0–10-cm soil layer (Fig. 6), with no clearrelationship between soybean production and either soil pH(Fig. 6), base saturation (Fig. 6b) or aluminum saturation (Fig. 6c).

Fig. 6. Relationship between relative soybean yield and soil pH (a), base saturation (b) andwith and without surface lime reapplication, for a long-term no-till integrated crop-livest(D). Lime was reapplied in May 2010. The entire area was surface broadcast with lime

Notably, such relationships are very clear for conventional tillagesystems (with plowing and disking) and even for the early years ofNT systems (Pearson and Adams, 1967; Sumner, 1997).

On the other hand, it is important to note that the highestabsolute values of soybean yield were obtained under the moreacidic conditions observed in this study (2010/11 cropping season,6–12 months after lime reapplication). However, this croppingseason had the highest rainfall among the three analyzed (Fig. 1a).Thus, water was the key factor determining the differences inproduction between the years studied, and not the soil aciditystatus; the amounts of rainfall (Fig. 1a) and the soybean yields inthe growing seasons evaluated (Table 2) had a positive andsignificant linear relationship (R2 = 0.98, p < 0.05).

4. Discussion

Our study considers a region of great interest for world foodproduction: the subtropical region. In Brazil, almost half of the totalgrain production is located in the subtropics, with approximately11 million ha under NT for summer crops (mostly corn and soybean).Although this region does not experience a dry winter season (asdoestheBrazilianSavannah–“Cerrado”),only2.1 millionhectaresarecultivated with crops during winter (CONAB, 2013), with a large area

aluminum saturation (c), for the 0–10-cm soil layer, before soybean seeding in areasock system (soybean-beef cattle) under intensive (*), moderate (&) and no grazing

in the beginning of the experiment (2001).

Table 2Soybean yield in growing seasons after surface lime reapplication (performed inMay of 2010) to a long-term no-till integrated crop-livestock system (soybean-beefcattle) under varying grazing intensities. The entire area received surface liming inNovember of 2001.

Grazing system Lime reapplication Average

With Without

2010/11 growing season, 6–12 months after lime reapplication, Mg ha�1

Intensive grazing 3.27 3.33 3.30Moderate grazing 3.03 3.03 3.03No grazing 3.83 3.10 3.47Average 3.38 3.16

2011/12 growing season, 18–24 months after lime reapplication, Mg ha�1

Intensive grazing 0.25 Ba 0.18Cb 0.21Moderate grazing 0.27 Ba 0.26 Ba 0.27No grazing 0.41 Aa 0.42 Aa 0.42Average 0.31 0.29

2012/13 growing season, 30–36 months after lime reapplication, Mg ha�1

Intensive grazing 2.41 2.77 2.59 BModerate grazing 2.52 2.58 2.55 BNo grazing 2.91 2.85 2.88 AAverage 2.61 2.73

Accumulated in the three growing seasons after lime reapplication, Mg ha�1

Intensive grazing 5.92 6.28 6.10Moderate grazing 5.83 5.87 5.85No grazing 7.15 6.37 6.76Average 6.17 6.30

Tukey test, p < 0.05: Lower case letters distinguish, in the lines, the limereapplication in each grazing system; upper case letters distinguish, in thecolumns,grazing intensities with or without lime reapplication (absence ofletters=no significant difference).

148 A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149

(approximately 4.0 million hectares) containing cover crops of highforage potential. Thus, the introduction of animals into such areas(e.g., beef cattle) during the winter is an interesting alternative toincrease the land use efficiency for food production and farmers’profitability. However, some questions need to be answered todiminish the resistance of grainproducers to introducing livestock incropping areas. Two of the many question topics were evaluated inour study: the effect of grazing intensity on lime movement throughthe soil profile and the impacts of grazing on soybeanyields – with orwithout lime reapplication.

Regarding lime movement through the soil profile, our resultscorroborated those of Flores et al. (2008) found previously for thesame trial when the first surface liming was performed: grazing,regardless of its intensity, does not restrict lime movementthrough the soil profile. In contrast, grazing enables surface limingto affect deeper soil layers, as observed for all the soil acidityattributes evaluated in the present study (Figs. 2, 3 and 4). Thegrazing treatments evaluated (IG and MG) were associated withamelioration of soil acidity, as measured by soil pH, for at least a10 cm greater depth compared to the NG treatment, for whichimpacts were only observed to a depth of 7.5 cm (Fig. 2b, d),compared to 17.5 cm for IG (Fig. 2b) and 20 cm for MG (Fig. 2d). Interms of base saturation, NG was also associated with the lowestimpacts to soil layers below the 10 cm soil depth (Fig. 3b).Regarding aluminum saturation, changes due to surface limingwere observed up to 40 cm under grazed conditions (Fig. 4b), butonly up to 17.5 cm in NG areas (Fig. 4c).

The differences observed for the liming impacts over the soilprofile, considering the evaluated acidity attributes, are the resultof distinct liming mechanisms. Specifically, the changes in soil pHdepend on the physical movement of fine lime particles throughthe soil profile, followed by the release OH� in the subsoil duringlime dissolution, as observed by Amaral et al., (2004b) in agreenhouse study. With the increase in pH, Al3+ precipitates andnew negative charge sites (CEC) are formed on soil solid phases,

which can be filled by Ca2+ and Mg2+ released from limedissolution. Thus, such a mechanism is responsible for theamelioration of acidity in terms of all the soil acidity attributesevaluated (soil pH, base saturation and aluminum saturation).

However, changes in base and aluminum saturation reacheddeeper soil layers because, for these attributes, another mecha-nism enables their higher mobility through the soil profile: thechemical mobilization by organic compounds. Under NTconditions, there is a decrease in the decomposition rate oforganic residues, preserving organic anions. Therefore, theseanions become available for leaching processes in which theyare paired with basic cations. In the subsoil, the cations may bereplaced by Al3+, which has a high affinity with organic ligands,thus becoming complexed (Miyazawa, 2000). Cassiolato et al.(2000), studying this mechanism under greenhouse conditionswith the same soil type as that of our study (an acidic Oxisol),verified that the effect of surface liming with black-oat residue(10 Mg ha�1) resulted in soil impacts to a depth of 25 cm, while thelime effect only reached a 10 cm depth without the residue.

In our study, the change in pH observed in the deeper layers inthe grazed treatments may have been associated with higher rootproduction under such conditions (Carvalho et al., 2011) and thepresence of dung beetles, increasing pore continuity and soilbioporosity and promoting the transport of fine lime particles.Furthermore, although grazing treatments were associated withlower amounts of remaining residue (Carvalho et al., 2011),hydrosoluble dung compounds have a high capacity for Alcomplexation in the soil solution (Haynes and Mokolobate,2001), as well as organic residue anions and root exudates,promoting the mobility of basic cations through the soil profile (Liuand Hue 1996). However, field studies are necessary to betterelucidate the reasons for the differential movement of limethrough the soil profile and the action of various mobilitymechanisms, especially under ICLS.

Despite the impacts of the treatments on acidity attributes afterlime reapplication resulting in higher D values (Figs. 2, 3 and 4),these impacts were not able to ameliorate soil acidity beyond the10 cm depth (Fig. 5), according to CQFS RS/SC (2004). This problemcould potentially be solved by surface liming at higher rates thanthat recommended, as observed by Caires et al. (2005) and alsosuggested by Conyers et al. (2003). However, because the soybeanyield only responded to lime reapplication for the IG treatment(Table 2) under severe drought conditions (Fig. 1), such a strategywould most likely not be economically viable.

The crop response to soil acidity (re)correction by surface limeapplication is still not sufficiently understood because it dependson soil acidity, liming rates, soil management and crop Alsensitivity (tolerance). In contrast to conventional tillage andshort-term NT, there is no direct relationship between liming andcrop yields under long-term NT, as observed in our study (Fig. 6).The soybean response to surface liming during the establishmentof NT systems in acidic, southern Brazilian Oxisols – for the sameregion and soil type of our study – has been found to range from6 to 88% (Oliveira and Pavan, 1996; Caires et al., 2003). On the otherhand, in a nine-year NT system, Caires et al. (2011) observedincreases in maximum yield from surface liming of onlyapproximately 13%, compared to no liming treatments (NTestablishment). Regarding the latter, Brown et al. (2008) hasexplained the lack of crop response to liming under long-term NTconditions by the effects of soil pH buffering, which results fromresidue decomposition, and Al complexation in both solid andliquid soil phase. Thus, Al dynamics under ICLS is a subjectdeserving further investigations.

According to Sá, (1999), NT systems progress through varioussteps until reaching consolidation (>10 years), starting with soilstructural rearrangement, microbial biomass establishment and crop

A.P. Martins et al. / Soil & Tillage Research 144 (2014) 141–149 149

residue accumulation. Thus, gradients in carbon and nutrientsgradient will form (stratification) in the topsoil and the soil CEC willincrease, resulting in continuous nutrient and water cycling. Thepresent ICLS trial was established 12 years ago; yet, the area has beencultivated under NT for 20 years, enabling it to be considered aconsolidated NT system. From this perspective, crop and soilresponses are not just described as “cause-effect” because matterand energy fluxes determine the soil “auto-organization process”with a dominance of interaction effects over isolated impacts(Addiscott,1995; Vezzani and Mielniczuk, 2009). Therefore, consoli-dated NTsystems are buffered and less dependent on external inputswith low or null crop responses to fertilization applications and soilcorrection practices. The results observed for the lime reapplicationin our study reinforce such a theory because liming was consideredan essential procedure for cultivation in acidic soils.

5. Conclusions

Soil correction in deeper layers after the surface limereapplication is not restricted by intensive or moderate grazing(10 or 20 cm sward management height, respectively) undermanagement as an integrated soybean-beef cattle system. Instead,grazing provides increased amelioration of soil pH, base saturationand aluminum saturation in deeper layers, compared to non-grazed areas. The timing of the greatest impacts of limingreapplication varies. However, under soybean-beef cattle integra-tion, the greatest impacts are, in general, observed after the grazingperiod (winter season). Such dynamics characterize the chemicalresilience of the soil, with more acidic conditions occurring afterthe soybean season for such food production systems.

Under long-term integrated conditions, the soybean yield is notaffected by soil acidity attributes. The impacts of broadcast limereapplication for the integrated system are only significant undersevere drought and intensive grazing conditions. However, whenthe rainfall during soybean cultivation is lower than the expectedclimatological normal, non-grazed areas have higher soybeanyields, regardless of lime reapplication.

Acknowledgements

We would like to thank Adao Luis Ramos dos Santos for thesupport provided in the laboratorial analysis and field activities. Wealso thank the National Council for the Development of Science andTechnology (CNPq) and the Coordination for the Improvement ofHigher Education Personnel (CAPES) for financial and scholarshipsupport

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