SEED RATE AND ROW SPACING OF NO-TILL WINTER-WHEAT

A snow management system, which utilizes no-till seeding into standing stubble immediately after harvest of the previous crop, has permitted the expansion of winter wheat (Triticum aestivum L.) production in western Canada. The effect of seed rate and row spacing on grain yield and yield components of no-till winter wheat were evaluated in 21 trials conducted in Saskatchewan from 1986 to 1988. Two winter wheat cultivars were evaluated in eight of the trials. The relationship between grain yield (Y) and seed rate was best described by a modified inverse polynomial: Y = uSR(1-SR/566)/(SR + u/104) where u represents the upper limit of yield when seed rate is not limiting. This curve accounted for 98% of the observed variation in grain yield. Optimum seed rate varied from 58 kg ha-1 at a very dry trial to 148 kg ha-1 in a trial with more favorable growing conditions. Grain yield increased as row spacing decreased and the effect of row spacing on grain yield was increased under more favorable growing conditions. Increased seed rate and decreased row spacing interacted positively to increase grain yield so optimum seed rate increased as row spacing decreased. Increased spikes per square meter was responsible for the increase in grain yield associated with high seed rate and narrow row spacing. In contrast, kernel weights were slightly higher with low seed rate and kernels per spike were higher with low seed rate and wide row spacing. Optimum seed rate was higher for the cultivar 'Norstar' than for 'Norwin' due to higher yield potential of Norstar under the conditions experienced in this study.