Effect of preplant/early irrigation, nitrogen and seeding rate on winter wheat grain yield

Preplant or early irrigation in winter wheat (Triticum aestivum L.) can improve plant stands and lead to higher grain yields. Optimum seeding density more efficiently utilizes resources and optimizes yield. In lieu of groundwater storage continuing to decline, more precise and efficient utilization of water is needed. Wheat experiments were conducted to evaluate nitrogen (N) rate, seeding rate and early irrigation over three growing seasons near Stillwater, Oklahoma. Experimental design was a split-split plot with 3 replications and nine treatments, with irrigation as the main plot. Seeding rates of 45, 67 and 112 kg ha-1 were sub plots and that included three N rates (0, 67, 134 kg ha-1) as sub-sub plots. Tiller count, head count and grain yields were collected. Mid-season biomass and harvest index were recorded. Results showed that, for different cropping seasons, grain yield, biomass, tillers, heads, grain N and harvest index depended either on the interaction effect or main effect or both. Early irrigation did not affect grain yield. Seeding rate and N rate were significant for number of heads. Midseason biomass weight was significant with irrigation. Harvest index was not significant for irrigation, seed rate and N rate or interaction effects. Grain yield response to irrigation varied considerably due to differences in rainfall received during the cropping season. This study showed for the given environmental conditions, early irrigation has no effect on winter wheat grain yields