Tiller Initiation and its Effects on Yield and Yield Components in Winter Wheat

Vegetative growth in the form of tillers is crucial to final yield in winter wheat (Triticum aestivum L.). To understand the impact management practices have on tiller initiation, a study was conducted using two seeding rates (1.9 x 10(6) vs. 6.8 x 10(6) ha(-1)) and two N timing applications (single vs. split). Tillers initiated in the fall made up the majority of spikes compared to tillers initiated from 1 January to the start of jointing (GS 30). Tillers initiated in March at either seeding rate produced very few kernels spike(-1), low kernel weight, and contributed little to yield. At the high seeding rate, tillers initiated prior to 1 January were responsible for more than 87% of the grain yield. Tillers produced in January- February produced 5 to 11% of the final yield, while tillers produced in March contributed less than 2%. In contrast, at the low seeding rate tillers produced in January-February made up 20 to almost 60% of the final yield. Overall, this study shows the timing and rate of leaf initiation impacts yield and yield components. Earlier tillers have an advantage in that they have shorter periods of leaf development that result in more leaf area which in turn supports more kernel spike(-1) and heavier kernels, thus more grain weight per spike. Timing of N (single vs. split) application resulted in no significant impact on tiller development, spike number, kernel number, kernel weight, or grain yield.