Effect of Preplant/Early Irrigation, Nitrogen and Population 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 view of groundwater storage continuing to decline, more precise and efficient utilization of water is needed. Wheat experiments will be conducted to evaluate nitrogen (N) rate, early irrigation and planting density over three growing seasons near Stillwater, Oklahoma.  A split-plot experimental design was used with irrigation as the main plot. Seeding rates of 45, 67 and 112 kg ha^-1 will be evaluated and that include 3 N rates (0, 67, 134 kg ha^-1).  The experimental design included 3 replications and 9 treatments, with plot sizes being 3.1 x 6.2m. Preplant irrigation was applied using mobile sprinkler units. Green Seeker Normalized Difference Vegetative Index (NDVI) will be recorded for different growing stages. Head counts and grain yields will be collected. Mid-season biomass and harvest biomass will be recorded. Nitrogen use efficiency (NUE) will be calculated for each treatment. Analysis of variance will be used to detect significant differences between main effect and treatment interactions at early growth stages, for grain yield, grain N, harvest index, biomass and NUE. Results should show higher yield and NUE for the irrigated plots. Treatments evaluated should highlight practices that optimize grain yield.