INFLUENCE OF TILLAGE ON PLANT-POPULATIONS, DISEASE INCIDENCE, AND GRAIN-YIELD OF 2 SOFT RED WINTER-WHEAT CULTIVARS

No-till soft red winter wheat (Triticum aestivum L.) production reduces soil erosion and increases the opportunity for timely planting. The purpose of this study was to determine if the elimination of tillage in winter wheat production influences plant populations, disease incidence, and grain yield response to N fertilization. A 3-yr study was conducted on a Loradale silt loam (fine, mixed, mesic Typic Argiudolls) using two cultivars. No-tillage (NT) was compared to more conventional (CT) systems involving either a moldboard or chisel plow. Fertilizer application rates were 0, 70, and 140 lb N/acre. Plant stands for the cultivar 'Caldwell', measured 3 wk after planting, were 14.7% lower in NT than in CT in 1982-1983. Plant stands for both cultivars were 12% lower in the NT system in 1983-1984. The incidence of powdery mildew (Erysiphe graminis) was higher under NT in 1982-1983, while septoria glume blotch (Septoria nodorum) infection was not affected by tillage. Powdery mildew infection was greatest for the cultivar 'Wheeler' while septoria glume blotch infection was greatest for Caldwell. Lodging was greater in the NT system in 1982-1983. Lodging was higher for Wheeler in NT than in the CT system in 1982-1983. Flag leaf and grain N concentrations were not influenced by tillage system in any season. Grain yields responded positively to N application 2 of the 3 yr, but were not affected by tillage system in any year. A tillage X N rate interaction for grain yield was not observed. Efficiency of fertilizer N removal by grain (corrected for controls) averaged 43% at 70 lb N/acre and 29% at 140 lb N/acre.