MANAGEMENT EFFECTS ON YIELD AND YIELD COMPONENTS OF LATE-PLANTED WHEAT

Intensive cereal management can increase the yield and performance of winter wheat (Triticum aestivum L. emend. Thell.), but wet soils often delay planting along the Gulf Coast. Field experiments were conducted at four locations in 1991 and two locations in 1992 to evaluate the e ffects of two seeding rates (84 or 168 kg ha(-1)) and two topdress N r ates (90 or 90 + 45 kg ha(-1)) for an early and late-maturing cultivar planted at a recommended date or 35 d later. Main effects were genera lly more significant than interactions except for those involving envi ronment (year-location). Late planting resulted in a significant reduc tion in grain yield even though more spikes per square meter were prod uced. Wheat kernels from the recommended planting date were heavier an d each spike contained more kernels, which resulted in higher grain yi eld. Additional N significantly increased yield when the crop was plan ted at the recommended date by increasing kernels per spike and spikes per square meter, but did not increase yield of the late-planted crop . Grain yield was not affected by seeding rate for the early planted w heat. Seeding rate effects were influenced by the environment for late planting; however, there was evidence that the higher seeding rate in creased yield of the late-planted crop. Delayed planting reduced yield s due to a decrease in kernel weight and kernel number per spike, but the magnitude of yield loss was reduced by using an early-maturing cul tivar and a higher seeding rate.