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

The primary goal of this study is to evaluate the impacts of timing and rate of N fertilizer application on wheat grain yield and protein content, while reducing the potential for N loss. The study focuses on hard and durum classes of spring wheat grown in California, and will span three years, employ two experimental approaches, and include multiple varieties and locations across California’s diverse wheat agro-ecosystems.

Since high wheat yields are often accompanied by low protein content, the combination of high yields and high protein content can be difficult to achieve, particularly with some of the newer, higher-yielding varieties. This can serve as a significant incentive for growers to apply high rates of N fertilizer in order to increase the likelihood of achieving desired grain protein percentages. Five experiments have been conducted at three locations. Data analysis is underway.

Primary objectives of this research include: 1) compare the yield and protein content of the most popular hard red, hard white, and durum spring wheat varieties in response to a range of N application treatments to determine their N use efficiency; 2) evaluate N management schemes utilizing different rates and split applications of N to determine the effectiveness of pre-plant applications versus delayed applications to more closely match plant uptake in three wheat-production regions in California; and 3) determine the concentration of soil nitrate remaining in the profiles at the end of the season as a function of fertilizer practices.

Additional objectives include evaluation of soil nitrate quick tests and plant tissue tests in providing information regarding fertilization practices.