Variation in Nitrogen Use Efficiency and Nitrogen Response in Winter Wheat Varieties Common to the Central Great Plains.

Increasing nitrogen use efficiency (NUE) in winter wheat can help producers maximize benefits of nitrogen fertilizers and reduce environmental risk of N loss. Many studies have investigated management impacts on NUE, however very few have investigated effects of crop genetics. The objective of this study was to determine if there are differences in NUE among 30 wheat varieties commonly grown in the Great Plains. The experiment was a field study in Rossville, Kansas with treatments consisting of N rate and variety. The wheat varieties were grown with two N rates, 0 kg N ha-1 and 100 kg N ha-1. Nitrogen use efficiency was calculated as the grain yield per unit of available nitrogen (sum of soil N and fertilizer N) and was significantly affected by variety (p=0.028). Several other related parameters, such as nitrogen utilization efficiency, nitrogen remobilization efficiency, and biomass production efficiency were also significantly affected by variety (p<0.05). These data suggest that there are significant genetic differences among varieties. A second nitrogen response study with four select varieties, including a full-height variety, was planted near Silverlake and Manhattan, KS. Wheat received four nitrogen rates, 0, 34, 90, and 146 kg N ha-1. Nitrogen rate and variety both significantly affected grain yield (p=0.045), however the pattern of N response was different at the two locations. The results of these two studies suggest that there are significant differences in NUE and nitrogen response among winter wheat varieties. This information could potentially be used by breeders to develop more efficient crops that would maximize benefits of fertilizer inputs and reduce negative environmental impacts.