Response of Winter Wheat to Simulated Stand Reduction

Environmental stresses can reduce winter wheat (Triticum aestivum L.) stands to less than optimum densities, forcing producers to assess yield potential from early season plant densities. Our objectives were to assess changes in yield and associated traits resulting from varying spring plant densities, and to determine if these responses varied by cultivar. Three hard red winter wheat cultivars were grown at seven population densities in seven Montana environments. Plant density levels ranging from 10 to 100% of target stand were achieved for each cultivar by planting 215 seeds m−2 in the fall and replacing winter wheat seed with spring wheat seed in proportion to the desired spring survival for each treatment. Cultivars did not differ in mean spring plant density or grain yield but differed for yield components, test weight, and protein concentration. The response to increasing plant density was generally not cultivar specific, as plant density interactions with cultivar were significant only for kernels spike−1. Grain yield increased, as did spikes m−2 and kernels m−2, while kernel weight and kernels spike−1 decreased with increasing spring plant density. Response to increasing spring plant density varied with environment for all traits, but environment effects and linear and quadratic plant density terms accounted for 95% of the variation in interaction means for all traits except tillers plant−1. Maximum grain yield occurred at 140 plants m−2, and 21.5 plants m−2 produced winter wheat grain yield equal to spring wheat grain yield for the same environments.