Monday, November 5, 2007 - 10:20 AM
100-3
Nitrogen Recommendations for Corn: A Northeastern Perspective.
Nitrogen recommendations for corn in most states in the Northeast US currently follow a similar approach. The base recommendation is usually determined from the yield potential. Most states use 1 lb N/bu expected yield for this base recommendation. Several states do not use yield potential or only use it to modify the base recommendation. This base recommendation is commonly adjusted for previous legumes and residual N from past manure applications. Some states adjust for soil properties such as soil type, organic matter, and soil drainage. Recommendations are typically made for fertilizer N. However, since manure and other organic sources of N are widely used in the region, all states have a system for converting the fertilizer N recommendation into an organic source recommendation. The pre-sidedress soil nitrate test has been widely adopted in the region. This test is especially useful for making in-season N adjustments on manured fields. Some states use the chlorophyll meter test for the same purpose. The late season stalk nitrate test has been adopted by several states to provide feedback on corn N management for fine tuning future N recommendations. States in the northeast have been looking at ways to improve recommendations and are evaluating the amino sugar N test, there is ongoing research using on-the-go active reflectance sensors, and there has been a general evaluation and discussion across the region of how recommendations are made and presented to growers. Because of the extensive use of manure and legume crop rotations, the approach has been moving away from a simple fertilizer rate recommendation based on yield, to a more integrated system that accounts for crop, soil, weather, and economic factors in a stepwise process that begins with site specific estimates of N required followed by adjustments based on testing and other information such as weather, crop rotations, manure applications, etc.
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