Wednesday, November 15, 2006

Rescue Nitrogen Applications for Corn.

Kelly Nelson1, Peter Scharf2, William Stevens3, and Bruce A. Burdick2. (1) Missouri University, Greenley Research Center, PO Box 126, Novelty, MO 63460, (2) Univ of Missouri, Dept of Agronomy, 214 Waters, Columbia, MO 65211, (3) Univ of Missouri, Delta Center, PO Box 160, Portageville, MO 63873

Rescue nitrogen (N) applications in a standing corn may be necessary when wet conditions prevent preplant N applications or loss of N was suspected due to wet conditions after application.  Field research at Albany, Columbia, Novelty, and Portageville in 2003 and 2004 evaluated the impact of ammonium nitrate (AN), urea ammonium nitrate (UAN), urea, and urea plus urease inhibitor, N-(n-butyl) thiophosphoric triamide (NBPT) applied broadcast and between-row (BR) as a preplant or postemergence application to 30-, 60-, 90-, and 120-cm tall corn.  Nitrogen applied BR injured corn on average less than 5% 7 days after treatment except UAN applied to 60-cm tall corn.  Broadcast applied N injury was ranked UAN (32-55%) > AN (14-26%) > urea (4-8%) = urea plus NBPT (5-10%).  BR application of AN, UAN, or urea plus NBPT to corn 30- to 120-cm tall had optimal grain yields at 60 to 100% of the sites; however, BR application of urea was consistent at 80 to 100% of the sites when applied to 90- to 120-cm tall corn.  Broadcast applications of N sources with optimal grain yields at 60 to 100% of the sites included UAN up to 30-cm tall, AN applied to 30- and 60-cm tall, and urea or urea plus NBPT applied from 60- to 120-cm tall.