Keywords: Wheat, oilseed rape, peas, yield, radiation use efficiency, water use efficiency.
This paper has estimated the potential yield for winter wheat, winter oilseed rape and spring peas for the UK environment using three methods; 1) extrapolating current yield trends, 2) estimating the maximum potential biomass accumulation and greatest partitioning to the seed and 3) a detailed physiological approach considering the extent to which the critical phases of growth may be extended and growth rates increased. On-farm yield trends were either flat or increasing very slowly which may indicate that the yield potential for the UK environment is being approached. However, the rate of improvement of new varieties was continuing which indicated that the yield potential was not being reached and changes to farm practice have prevented the greater genetic potential of new varieties from being realised. Estimating yield potential using methods 2 and 3 gave similar results with average yields for the two methods in an environment without water limitation of 18 t/ha for winter wheat and 9 t/ha for winter oilseed rape and peas. A consideration of the average rainfall and the amount of plant available water stored in soil indicated that these potential yields could not be achieved on soils with below average available water capacity (AWC) and in dry regions of eastern England. After crudely taking account of the water availability the potential yields for the main arable areas were estimated at 17 t/ha for winter wheat and 8.5 t/ha for winter oilseed rape and peas. In the driest regions with low AWC soils the potential yields would be 14 t/ha for wheat and 6 t/ha for oilseed rape and peas. Constraints for achieving these potential yields include; climate change — particularly greater temperatures and reduced water availability, low product prices relative to input costs and environmental regulation both of which can result in sub-optimal input levels and restrict the uptake and development of new technology.
P M Berry, ADAS High Mowthorpe, Duggleby, Malton, N Yorkshire YO17 8BP, U.K.
R Sylvester-Bradley and R Weightman, ADAS Boxworth R and D Centre, Boxworth, Cambridge CB3 8NN, U.K.
27 pages, 4 figures, 2 tables, 63 references.