Optimizing Water and Nitrogen Use for Sustainable Wheat Production

View the project final report

• 2016 annual report

Commodities

• Agronomic: wheat

Practices

• Crop Production: irrigation, nutrient cycling, application rate management
• Production Systems: general crop production

All field and lab based activities have been completed. The study was conducted at two locations in Idaho and one location in Montana. Several research and extension publications have bee released for publication. Two research publications are currently in review. One is focused on the water and nitrogen in relation to wheat crop yield and the other - focused on wheat root growth and development. Extensive number of wheat root samples has been analyzed and will allow for comprehensive peer-reviewed paper. In our experiments conducted in 2016 and 2017, soil residual nitrogen (N) at 0-2 feet prior to planting ranged from 80 to 130 lb N/acre, which allowed for more N application to increase grain yield, according to the University of Idaho guideline for hard spring wheat fertilization under irrigated conditions. However, one hard white and one hard red varieties of spring wheat failed to show increases in grain yield in response to various N rates from residual N (zero N application) to a high N rate of 250 lb/ac (soil residual N plus N application) (Yang et al., 2018). Consistently, aboveground biomass and its N concentration at harvest were not different among the N rates.
These results may suggest that N applications overtime have built up soil N fertility, and residual N from previous crops might be plenty for the following wheat crop. For N fertilization, soil residual N is usually quantified at 0 to 1 or 0 to 2 feet, whereas the root system of wheat can reach as deep as 6 feet. Thus, soil residual N located at 3 to 4 feet can be used by wheat, which is seldom counted towards N input. On the other hand, to improve grain yield, N uptake has been genetically increased through breeding efforts over the last a few decades, so the N requirement for optimal yield in recently developed varieties may not be as high as old varieties. Thus, it is imperative to investigate N requirement for optimal grain yield with considerations of soil residual N from a deep soil profile and differences in N uptake among recently developed varieties.  We plan to continue working on identifying best management strategies for wheat.

• To evaluate the effects of N rates and drip-irrigation treatments on hard red spring wheat plant growth and yield
• To develop sensor-based methods to predict yield and grain protein content in varying N and water environments, and to determine the minimum N and water required to maintain wheat grain yield and quality
• To develop empirical models predicting yield loss due to N stress and yield loss due to water stress