Corn Yield Response to Fall and Spring Applied Controlled-Release Urea vs. Spring Conventional Urea.
Jeff Moore1, Randy Killorn2, and Marianela Gonzalez1. (1) Iowa State Univ, Dept of Agronomy, Ames, IA 50011, (2) Iowa State Univ, Agronomy Dept, 3208 Agronomy Hall, Ames, IA 50011-1010
Nitrogen (N) application to corn has been proven to increase yields, but concerns about nitrate-Nin ground and surface water have led to investigation of controlled-release N fertilizer. The objective of these experiments is to compare corn grain response to controlled-release urea (ESN) and conventional urea. Two field studies are being conducted at two locations in Iowa and corn yield data will be reported from 2003-2005. All N treatments were hand broadcast in 34 kg N ha-1 increments from 0 kg N ha-1 to 202 kg N ha-1, then incorporated into the soil using standard tillage practices for the area. In the spring study, grain yield increased with N rate at all locations every year and there were significant differences due to N material at four of five site-years. Average grain yields were 9.5 Mg ha-1 for the ESN and 9.2 Mg ha -1 for the conventional urea. In the fall study, grain yield increased with N rate at all locations every year and there were significant differences due to N material at two of three site-years. On average, grain yields were 9.6 Mg ha-1 for the fall applied conventional urea, 9.8 Mg ha-1 for the fall applied ESN, and 10 Mg ha-1 for the spring applied conventional urea.