|YOST, MATT - University Of Minnesota|
|COULTER, JEFFREY - University Of Minnesota|
Submitted to: Forage Focus
Publication Type: Trade Journal
Publication Acceptance Date: 4/26/2013
Publication Date: 5/1/2013
Citation: Yost, M.A., Russelle, M.P., Coulter, J.A. 2013. Improved predictability of fertilizer nitrogen need for corn following alfalfa. Forage Focus. May 2013. p.18, 21.
Technical Abstract: Accounting for alfalfa nitrogen (N) credits to first-year corn reduces fertilizer N costs, over-application of N, and the risk of nitrate loss to ground water. It is equally important, however, to avoid inadequate N supply for corn. We analyzed nearly all previous research on fertilizer N response in first-year corn following alfalfa, comprising 288 fields in North America covering a wide range of weather, soil, and crop management conditions. On coarse-textured soils, fertilizer N was almost always needed to optimize grain yield of first-year corn after alfalfa. We speculate that N loss by leaching is the leading reason. In contrast, fertilizer N was required to optimize first-year corn grain yield in only 18% of fields with medium-textured soils and in 47% of fields with fine-textured soils. The higher number of responsive fields with fine-textured soils may have been due to delayed N mineralization and increased denitrification when soils were wet. On coarse-textured soils, only 1 of 25 fields did not need fertilizer N, but more field research is needed to predict that unusual situation. For medium- and fine-textured soils, we could correctly identify the need for fertilizer N in 75 to 89% of the cases using prediction models that include alfalfa stand age and weather conditions prior to corn planting. Where fertilizer N was needed, the economically optimum N rates varied widely for all soil texture groups. We are working to refine predictions of these optimum N rates, and will produce a tool to help growers know which fields need fertilizer N and how much to apply.