Aspects of Applied Biology 109, 2011Agricultural Ecology Research: Its role in delivering sustainable farm systems

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Developing strategies for the improved utilisation of local- and site-specific trace element resources to enhance crop and livestock

quality

By R L WALKER1, A C EDWARDS1, I ÖBORN2,3, C CAMPBELL2,3, M COULL3, S DAHLIN2, J ERIKSSON2, B FRANKOW-LINDBERG2, S HILLIER3, B LINDSTRÖM1,2,

L LINSE2, A RAMEZANIAN2,3, D LUMSDON3, C SHAND3, A SINCLAIR1,C A WATSON1 and M WIVSTAD2

1Scottish Agricultural College (SAC), Aberdeen AB21 9YA, UK2Swedish University of Agricultural Sciences (SLU), SE-750 07 Uppsala, Sweden

3The James Hutton Institute, Aberdeen AB15 8QH, UK

Summary

This paper describes some aspects of a project whose objective is to develop sustainable strategies for local produce, with an emphasis on organic systems and trace element cycling. It aims to provide knowledge on soil management and crop species/variety selection in order to optimise trace element use in such systems. A range of trace elements have been considered, including B, Co, Cu, Fe, Mo, Mn, Ni, Se and Zn. Agricultural activities in Sweden and Scotland are the main project focus, with identification of areas and soil types in these countries with contrasting parent material and trace element concentrations a core aim. Linkages between these and potential trace element deficiencies of crops and livestock are being sought. The potential of common and novel forage species to provide components of ruminant diets based on their ability to take up/concentrate trace elements on contrasting soils are being investigated. This paper concentrates on the Scottish component of the project, and highlights information collated as part of the project’s reviewing process as well as the presentation of previously unpublished data.

Key words: Trace elements, herbage composition, soil, climate, management

Introduction

There have been recent trends for greater demand of both organic food (Willer & Klicher, 2009) and food with higher quality with an emphasis on local production and minimal “food miles- or carbon-footprints” (Henseleit et al., 2007). A research focus on how best to meet this demand is needed in terms of crop production that supplies both human and livestock needs. The emphasis placed on the local sourcing and production of feed and food for environmental reasons may inadvertently increase problems associated with crop health and quality, with these potentially linking to livestock and human health issues over the long-term (Kirchmann et al., 2009). This project is designed to minimise these potential adverse effects by providing information on the best management approaches for soil and crop species in order to supply optimum levels of micronutrients through the food chain at a local level. From baseline information on agricultural areas and soil types with contrasting parent material, the aim is to identify where micronutrient

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deficiencies in crops and livestock might be an issue, in particular when considering the impact of farm type, crop rotation and management on the micronutrient status in soils and the crops growing on them (including herbage). A key objective of the project involves an assessment of the factors which affect uptake of micronutrients by crops. Data obtained from the literature, long-term field trials and laboratory experiments are currently being collected and analysed to achieve this. This paper concentrates on the Scottish component of the project, and highlights information collated as part of the project’s reviewing process as well as a presentation of previously unpublished data from historically important experiments.

Materials and Methods

The systems nature of this research project requires a range of complimentary approaches to be deployed in order for the general objective, i.e. the sustainable utilisation of micronutrient supply to forage crops and ruminants, to be met. A range of data at the disposal of the research team is currently being interrogated for its applicability to the study of trace elements (micronutrients) in low input farming systems. This review has concentrated on factors likely to influence the composition of herbage/feed with particular emphasis on data having significance to Northern and temperate conditions. A selection of the main points that developed from this review are summarised here, and the general relevance towards the growing trend for local feed production is considered within this context. Much of the research originates from the 1960–70 period and therefore timed at the beginning of the general increase in use of N fertilisers and the move towards high biomass productivity.

Results

Herbage/feed quality represented a major issue for animal health during the period 1950–70s. Considerable research effort was directed towards identifying the underlying factors responsible for influencing the trace element composition and quality of herbage/feed. An indication of the potential ranges in composition of forage/feed collected from three regions of Scotland is shown in Fig. 1. Typically, these regions have different soil types, climates and consequently cropping systems that are broadly adapted to these.

Fig. 1. Range in copper and cobalt concentrations (mg kg-1 DM) in locally grown feeds in three Scottish Advisory Areas also showing SD and number of samples (from SAC/SARI, 1982).

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Factors likely to influence herbage composition A combination of site and management factors will be influential in determining mineral uptake and therefore quality of feed/fodder (Reith, 1965), these include: soil acidity; soil moisture or drainage conditions; soil temperature and seasonal effects; plant genus, species and variety; fertilization. The extents to which any of these individual factors are likely to influence herbage composition vary greatly (Fig. 2).

Fig. 2. Site and management factors likely to influence elemental composition of herbage.

Drainage (poor vs freely drained) Mitchell (1963) considered that poor drainage was the most important pedological factor influencing the mobilisation of trace elements in Scottish soils (see Fig. 3). Increased mobilization of Co, Ni, Cu and Mn in the gleyed sub-surface layers of poorly drained soils was observed, and this was accompanied by marked increases in herbage concentrations of Co and Ni.

Fig. 3. Comparison of extractable (acetic acid) trace elements for a freely (Insch Series) and poorly (Mosstown Series) drained soil profile developed from basic parent material (Insch Association). Data from Mitchell & Burridge (1979).

Soil pH The effects of pH on a range of trace element availabilities to typical forage species (perennial ryegrass and white clover) are shown in Fig. 4. While the actual magnitude of the pH effect will

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vary between soil type, as well as individual field management practices, the general trend will be typical for many soils.

Fig. 4. The effect of soil pH on the composition of (a) ryegrass and (b) clover grown on a long-term field experiment on a granitic soil in NE Scotland. Data are expressed relative to concentration of individual elements in plant material grown at pH 6, so the positive numbers represent an increase in concentration.

Individual plant species Some examples showing the range in trace element composition for species commonly present in a grassland pasture are presented. For example, Fig. 5 highlights the broad range of Co, Ni, Mo and Zn compositional differences of ryegrass and white clover growing on seven different Scottish parent soils. In addition, Table 1 presents data from some alternative forage crops (red clover and cocksfoot) as well as ryegrass that were grown on a freely drained soil derived from granitic parent material. The range in concentrations varies two-fold and while concentration of Co and Cu are higher in red clover, but Mn and Mo were higher in Cocksfoot.

Fig. 5. A comparison of grass/clover compositional data for cobalt, nickel, molybdenum and zinc from 75 ‘on-farm’ field experiments (during the late 1950s) located in NE Scotland and averaged across parent material (unpublished data). Error bars represent SE. OA - Ordley Association; ORS – Old Red Sandstone; S&G – Sand and Gravel.

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Table 1. Concentration (mg kg-1 DM) of three species from a mixed sward growing on a granite soil (Mitchell, 1960)

Co Cu Mn MoPerennial ryegrass 0.2 6 59 0.32Cocksfoot 0.14 5.8 101 0.53Red clover 0.26 17.5 56 0.35

Differences in growth patterns of each species during the year (Fig. 6) will also introduce a further source of variability in composition and potential feed quality which may or may not match the livestock trace element requirement at that particular time.

Fig. 6. Copper contents of grasses and clovers, plants grown in single mixes. Data from Fleming (1965). (RSMG – rough stalked meadow grass).

Discussion

Together the factors described highlight a number of the key background components that result in the wide variation of trace element composition that have been measured in forage species. It also indicates why local sources of herbage are likely to vary in their trace element composition, with potential health effects on the livestock being fed predominantly on this, which could be either positive or negative. With this underlying knowledge, in conjunction with information being derived in other aspects of the project, e.g. improved understanding of trace element cycling/budgets under different management systems and information on local sources of re-cycled soil amenders with elevated trace element concentrations, weaknesses in the system can be identified and addressed. The total quantity of each element ingested will depend upon the relative biomass of each species present in the diet as well as its trace element concentration. ‘Dilution’ effects need to be taken into consideration in terms of trace element uptake in any livestock diet and the likely effect this will have on the animal’s health. The results generally suggest that inclusion of clovers and other species in a sward are likely to increase the trace element uptake of the forage. McKenzie et al. (2003) observed that the application of N fertiliser to non-organic grassland will reduce the clover content of the sward, moving it more towards a pure stand of predominantly ryegrass (in most cases). A move towards greater biomass production by applying greater quantities of N to grassland in conventional farms will need to be taken into consideration here. This has obvious implications in terms of the likely trace element content of the forage produced, although macro nutrients are likely to be less affected (McKenzie et al., 2003). Organic farms are prevented from using synthetic N, but can apply other bulky organic fertilisers such as farm yard

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manure and slurry. If trace element content of forage is seen as an issue on organic farms, or a farm attempting to use locally produced forage/feed, judicious use of these inputs will need to be made. On organic farms, the majority of N in the system is derived from N fixation by legumes e.g. clovers, with this N, and any other nutrients that have been taken up, being recycled either via livestock or as crop residues (Walker, 2010). Good management of trace elements on farm will involve accounting for the export of these (and other), nutrients either through produce sold off farm or from environmental losses (Owens & Watson, 2002).

Acknowledgements

The current project receives financial support from the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (FORMAS) (Contract 220-2007-1636) and the Swedish University of Agricultural Sciences (SLU). The Scottish Government has provided financial support to both SAC and the James Hutton Institute (previously the Macaulay Institute for Soil Research), at the time the historical experiments were undertaken from which the previously unpublished data presented here was derived.

References

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