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The aims of this project are two-fold. Firstly, to identify the factors that are constraining yield improvements of wheat and oilseed rape, and thus quantify the potential beneficial impact on yield of modifying agronomic practice. Secondly to identify the evidence gaps that need to be addressed before recommendations for improvements in agronomic practice can be fully delivered to the industry.

National and Recommended List variety trials are conducted under carefully managed conditions that differ from those in typical commercial farm practice in a number of ways. These differences provide an indication of some of the factors that might be limiting improvements of farm yields. Over the last decade there has been a general shortening of rotations on farm and the widespread adoption of non-inversion tillage which is not reflected in the trialling system. Pesticide and some fertiliser (e.g. sulphur) inputs are typically lower on farm, and inputs may be timed less effectively than is possible under trial conditions. The research proposed here will evaluate the relative contribution these factors may have made to the yield stagnation of wheat and oilseed rape in the UK. The following programme of research is proposed.

There is a considerable amount of year-to year-variation in average national yields which is likely to result from variation in weather conditions. This tends to obscure yield trends both in the United Kingdom and elsewhere in Europe. Thus the first step will be to separate, using statistical techniques, the effects of climate change and variable weather conditions on national average yields from those of crop management factors.

Trends in crop price, the cost of fertilizer and agrochemicals, and policy events will be analysed to determine the association between national yield trends and patterns of use of crop inputs. This will identify the key economic factors that have driven changes in agronomic practice and highlight possible barriers that will need to be overcome if recommendations for improvements in agronomy are to be adopted.

Data from the Farm Business Survey and that gathered specifically for this project from NIAB TAG and SAC farmer clients, will be used to determine whether the yield plateaux are associated more strongly with certain geographical regions or site conditions such, as soil type, or disease pressure. Then by comparing agronomic practices associated with the high yielding and low yielding farms within particular regions, or other groupings, the possible contribution of rotations, tillage, fertiliser and agrochemical inputs to the yield stagnation will be determined. The most influential factors will be the focus of the next stage of the analysis.

Results of field experiments, both published and unpublished, investigating the response of wheat and oilseed rape to rotation, cultivations, fertilizer and pesticide inputs and timings will be reviewed. In conjunction with information gathered on agronomic practice from commercial farms (described above), the scope for improving national average yield through improvements in agronomy will be estimated. This exercise will also reveal any gaps in evidence that need to be addressed. The likely impacts of proposed changes to agronomy on crop quality and the environment will be estimated and the potential barriers to uptake such as costs of implementation, practicality and farmer attitudes will be evaluated.
Consultation with industry representatives will be made at the outset of the project to help focus the research and when finalising its recommendations. The deliverable will be a list of immediate recommendations for change and key research and knowledge exchange priorities, to make short- and medium-term improvements to agronomic practice in order to increase farm yields of wheat and oilseed rape.
1: Examine existing evidence for agronomy as a contributory cause of yield plateau in wheat and oilseed rape, in the context of genetic improvement, climatic constraints, edaphic and other potential limitations, to define further the focus of the study.

2. Examine yield trends in the context of national data sets for crop price, cropped area, fertiliser usage and other agronomic factors.

3. Using farm specific data, identify trends in yield for shared character situations (profitability, soil type and condition, rotation, farming system, input usage), and investigate changes in farm or agronomic practice that may be related to yield trends.

4. Examine existing research evidence to quantify the likely yield impact of variation in, or changes to, farm practice or crop management and identify any strategic evidence gaps.

5. Assess the opportunities for overcoming yield constraints with respect to:
o Their relative importance
o Approaches to overcoming them (new research or knowledge transfer required)
o Constraints in achieving them (economics, legislation, farm practice, farmer behaviour)
o Their potential environmental impacts
o The potential impacts on quality and end use.

6. Report to Defra and utilise knowledge transfer opportunities to disseminate findings as appropriate.
Project Documents
• EVID4 - Final project report : IF01116- FINAL REPORT   (467k)
• TRP - Technical Report : Full technical HGCA report   (4076k)
Time-Scale and Cost
From: 2011

To: 2012

Cost: £27,553
Contractor / Funded Organisations
SAC Commercial Ltd, N I A B
Sustainable Farming and Food Science              
Sustainable Farming Systems