Effects of soil type on crop yield-weed density relationships between winter wheat and Bromus sterilis.
A range of densities of B. sterilis were sown in pots with winter wheat cv. Avalon in 4 soils; a heavy clay loam and a lighter, sandy soil from Oxfordshire and 2 sandier soils from Shropshire, and the effects of competition used to construct a model. B. sterilis emerged latest and yielded the least on the heavy Oxfordshire soil. Crop yield was also least on this soil, though there was no delay in emergence. These results may have been due to water logging. As a result, this soil gave rise to a distinctive crop yield-weed density relationship in which both crop yield and weed competitiveness were reduced compared with those on the other soils. Because of such differences in crop yield-weed density relationships, predictions of crop yield at a given weed density are considered likely to be imprecise unless the effects of soil type and climate are included in the model.