Competition among wheat plants sown at a wide range of densities

An experiment was undertaken with wheat (cv. Insignia 49) to study the effects of interplant competition on dry matter and grain production. Crops ranging in density from 1.4 to 1078 plants per sq. metre were established, and light intensity and growth measurements were made within the crop. Four sequential stages in the growth of the crop were recognized, namely: A period in which there was no interplant competition at any density. A period in which the crop growth rate showed a curvilinear relationship to the leaf area index and a linear relationship to light interception. A period when the weight of ears (early dough stage) showed a linear relationship to an expression involving the weight of green leaf in an earlier period and the percentage survival of tillers. A period of grain filling and ripening in which some further relative changes in ear and grain weight occurred. It is suggested that the application of this type of analysis to the reaction of different genotypes to crowding may add to an understanding of crop performance.