Effects of Soil Type on Crop Yield-Weed Density Relationships Between Winter Wheat and Bromus sterilis

Abstract

(1) An additive experimental design was used to study the effects of a range of densities of Bromus sterilis on the growth of winter wheat sown in pots containing soil from two fields at each of two locations in England. The pots were kept outdoors at a single site and crop and weed development was monitored. Yield data of both species were analysed by fitting non-linear models and comparing estimates of the parameters. (2) B. sterilis emerged later on the heavy Oxfordshire soil than on the other soils, and at the end of the experiment, the yield of B. sterilis was lowest on this one. The biomass yield of the crop was also least on this soil, though there had been no delay in emergence. 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. (3) It is possible that the different responses of the crop and weed on the clay soil were caused by waterlogging. (4) Because of such differences in crop yield-weed density relationships, predictions of crop yield at a given density are likely to be imprecise unless the effects of soil type and climate are included in the model.