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Fluid Journal : Fluid Journal 2005-2007
20 Fluid Journal FALL 2006 DRS. ALAN BLAYLOCK AND LARRY MURPHY SUMMARY Higher N prices and changes in materials available to crop producers have focused attention on NUE and management practices that can improve that efficiency. Surface N application in high-residue crops, particularly forages and topdressed small grains, has potential for significant losses by volatilization Optimizing N Management Without Ammonium Nitrate Nitrogen-use efficiency coming more into focus with the gradual phasing out of ammonium nitrate. Summary: Nitrogen (N) management options are changing as solid ammonium nitrate (AN) gradually is phased out of the supply chain for crop producers. For many individuals, AN has been the N source of choice for surface applications with high potential for ammonia volatilization. Several options are available for producers in those high-residue situations, including urea-ammonium nitrate solutions (UAN), N stabilizers, coated urea, and ammonium sulfate (AS). Specific placement of UAN has proven to be a highly valuable tool for improvement of N-use efficiency (NUE). Urea coatings and additives have also proven valuable in improving NUE by decreasing ammonia volatilization, controlling N immobilization on residues, slowing nitrification, and/or lowering leaching and denitrification losses. of ammonia. For years AN has been considered the standard as far as solid N sources are concerned and the choice of many producers faced with topdressing or surface applications in general on high- reside crops and reduced-till row crops. With transportation and storage of solid AN becoming a concern because of national security issues, a review of how other N sources (including UAN) can replace AN is in order. Placing it right Surface band. It's time to remind growers and dealers that strip placement of UAN for high- residue crops can be a valuable tool for improving NUE. Dribbling UAN as a surface band for forage crops, small grains, or no-till crops is a management option that has sometimes been overlooked and has several advantages, including: • Lowered possibility of foliage burn • Better responses to applied N • Lower volatility than broadcast urea or UAN • No soil disturbance • A widely available, economical N source. Cool season grasses, warm season grasses, and small grains all benefit from surface strip or dribble UAN applications. Just how much better strip applications may compare to broadcast applications depends on a number of factors: • Amount of surface residue • Type of residue
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