Improving winter wheat grain yield and nitrogen use efficiency using nitrogen application time and rate

Preplant nitrogen (N) application, which involves placing nutrients in the soil before seeding, has been an integral part of crop production systems for decades. Some producers are known to apply N at least 21 d before planting. This may increase N loss and lower grain yield. This study evaluated the effect of timing and rate of N application on winter wheat (Triticum aestivum L.) grain yield and N use efficiency (NUE). An experiment with a factorial arrangement of treatments was set up in a randomized complete block design with three replications. Treatments included four N rates (0, 45, 90, and 135 kg ha(-1)) with each applied 7 or 30 d before planting, and at Feekes 5 (FK5). Grain N was analyzed using LECO CN dry combustion analyzer. The difference method [Grain N from (fertilized plot - check plot)]/N applied was used to compute NUE. Nitrogen application rate significantly affected grain yield (P <= .01). Although the rate may be temporally and spatially variable, approximately 90 kg N ha(-1) was required to obtain yields that differ markedly from the check. Mid-season applied N (FK5) had similar yields to preplant applied N in two of four site-years and significantly increased yield at one site in 2020. Out of two sites, the timing of N application had a substantial effect on NUE in both years (P <= 0.11). In this case, NUE was increased by as much as 9.5% for midseason applied N compared to 30 d before planting N application time.