Nitrogen Management Strategies for Winter Wheat Yield and Grain Protein Improvement in Southeastern Colorado

Nitrogen fertilizer management is an important factor affecting wheat grain yield and protein content. The protein content in grain can often be improved by a N fertilizer topdress application later in the season. Where a premium is paid for grain protein, growers are more likely to adjust N management practices to improve this important quality parameter. Wheat production in Colorado has traditionally mostly been hard red winter wheat. But in recent years growers have been given incentive to plant more hard white wheat varieties, where a premium is paid for grain protein. As a result, white winter wheat acreage in the state has increased in recent years. This has caused more interest among growers in how N fertilizer can be used to impact grain protein. The objectives of this project are to i) develop N management strategies for optimum yield and protein content for dryland wheat production, ii) compare yield and grain protein responses of red and white wheat varieties to contrasting N rates and application timing, iii) determine if flag leaf N content, chlorophyll readings and GreenSeeker measurements are reliable predictors of yield and protein content, iv) evaluate the agronomic and economic performance of predicted N rates using the chlorophyll meter and GreenSeeker relative to common grower N rates, and v) develop and disseminate comprehensive N management guidelines for dryland winter wheat .

The experiment will be conducted at two farmer field locations in southeastern Colorado. Wheat variety (red and white), N application timing (pre-jointing and boot) and rate (40, 80 and 120 lb N/A) will all be evaluated. Phosphorus, K and micronutrients will be preplant applied according to soil test. Chlorophyll and NDVI (Greenseeker) readings will be taken at strategic times throughout the season, as will tissue samples for analysis for total leaf N content. Grain yield and protein content will also be determined. This research project was originally designed to start in the fall of 2012; however, drought and extreme temperatures resulted in a decision to delay the first planting until the fall of 2013. Total precipitation from July 2012 to June 2013 was only 6.6 inches, which is about one-third of the 30-year average. Most of southeastern Colorado wheat was lost due to severe drought and multiple freeze events. Support for the project is scheduled to continue.