Two cultivars of soft white winter wheat, Fredrick and Yorkstar, were sown at rates of 34, 67, 101, 134 and 168 kg/ha on or near 24 Sept., 9 Oct. and 23 Oct. in each of the 3 yr 1973–1975, at Ridgetown, Ontario. Highest net yields were obtained with rate of seeding 134 kg/ha. Seeding rate did not affect lodging. Yield per hectare and spikes per hectare were positively correlated while kernels per spike and spikes per hectare were negatively correlated. However, as the rate of seeding was increased, the increase in the number of spikes per hectare was greater than the accompanying decrease in kernels per spike, resulting in a net overall increase in yield. Highest yields of Fredrick were obtained near 9 Oct. and those of Yorkstar near 24 Sept. Yields decreased more rapidly with delayed seeding when seeding rates were less than 134 kg/ha, especially with Yorkstar. Test weight of Yorkstar was low, especially when sown late. Fredrick yielded 3–25% more than Yorkstar. A delay in seeding beyond 9 Oct. resulted in a yield reduction of 23 kg/ha/day. Fredrick should be sown instead of Yorkstar when seeding is delayed beyond recommended dates of seeding.
Ecophysiological modeling of yield and yield components in winter wheat using hierarchical bayesian analysis
