Effect of Nitrogen Fertilization Practices on Spring Wheat Yield, Protein Content

The goal of this study is to evaluate the timing and rate of N fertilizer application to optimize wheat grain yield and protein content, while minimizing the potential for nitrate leaching. Since high yields are often accompanied by low protein content, it can be difficult to simultaneously achieve both goals.

Field research to assess the response to N fertilizer management began during 2013 in the major durum, hard red, and hard white wheat-growing regions of California. Soil samples are collected to a depth of eight feet prior to planting and following grain harvest. Fertilizer application rates range from zero to 300 lb N/A, with adjustments for preplant soil nitrate concentrations. Nitrogen fertilizer is applied at a variety of times during the growing season (preplant, tillering, boot stage, and flowering stage) to determine how to maximize recovery. Various forms of N are being used to assess the right source to improve N uptake (including controlled-release N and various inhibitors). Plant tissue samples are monitored for various N parameters to improve the diagnostic techniques to make accurate fertilizer recommendations. This study will continue for several years to develop reliable N management strategies for wheat growers in this region.