Wednesday, November 7, 2007
297-12

Comparing Fall and Spring-applied N for Corn in Iowa.

Gaylia C.G. Ostermeier1, Tracy Blackmer2, Bradley Van De Woestyne1, and Peter Kyveryga2. (1) John Deere Company, John Deere, 4140 114th Street, Urbandale, IA 50322, (2) Iowa Soybean Association, Iowa Soybean Association, 4554 114th Street, Urbandale, IA 50322-5410

Fall-applied anhydrous ammonia is a common practice in the northern Corn Belt and sometimes results in N deficiencies in corn due to leaching and denitrification under certain conditions.  Currently, little data exists to identify when losses of N occur and the magnitude these losses.  On-Farm Network studies were established to compare fall and spring applications of N fertilizer at 58 sites during 2005 and 2006 in Iowa.  At each site anhydrous ammonia was applied to field length strips in the fall and adjacent strips received the same rate of N the following spring using guidance technology.  Spring N was applied as preplant anhydrous ammonia or sidedressed urea-ammonium-nitrate solution.  Strips were harvested with combines equipped with yield monitors and GPS.  Results showed that across many sites, yields of fall and spring-applied treatments were not different.  This suggests that either losses of fall-applied N were minimal or, if losses did occur, the rates used in the study exceeded the crop’s N requirements.  Minimal losses of fall-applied N may be more likely because of below normal spring rainfall.  To better assess the effects of early season rainfall on fall-applied N, additional studies are needed in years that experience varying amounts of early spring rainfall.

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