Using a Mail Survey and Spatial Statistics to Define Nitrogen Management Zones for Hard Red Spring Wheat in Minnesota.

Nitrogen is the single most important nutrient to improve yield in any non-legume arable cropping system.  This is especially true for Hard Red Spring Wheat (HRSW) where producers demand maximum grain yield and the market demands a minimum grain protein content.  Analogous to yield, nitrogen is also the first rate limiting nutrient for grain protein.  It is therefore paramount to have the best possible nitrogen recommendations for HRSW to optimize both yield and protein. Minnesota’s current N recommendations divide the state in two N management zones; an eastern zone where the soil nitrate test is not used and a western zone where the soil nitrate test is used to establish recommended fertilizer N rates.   The current N recommendations in the western zone, shared with North and South Dakota, were based on 69 individual nitrogen rate response trials across this target area.  The variability in the original 69 site-year data as well as anecdotal evidence of growers suggests considerable geospatial variation across Minnesota’s western HRSW N management zone. Therefore, it is warranted to explore this variation in more detail, a prerequisite to more nuanced N management recommendations in the future.   The objective of this research is to develop interpolation maps of observed variability in grain protein content across the Western HRSW N management zone and define potential sub- zones as a first step to improving the N management recommendations for HRSW. Results of the initial mail survey to growers will be shared.