ABSTRACT

Split nitrogen (N) application has been determined to reduce excess application of N fertilizer and increase nitrogen use efficiency (NUE). However, the effect of placement distance of the mid season (V8) applied N on corn yields and NUE has not been extensively evaluated. To address this concern, a field study to evaluate midseason (V8 to V10) variable liquid UAN (28%) rates of 45, 90,134, and 224 kg N ha^-1) applied at different distances (0, 10, 20, 30 and 38 cm) within the row on corn grain yield and nitrogen use efficiency was established at Haskell and Hennessey in 2009 and Efaw and Lake CarlBlackwell in 2010.The experimental design was a randomized complete block design, with 3 replications. From V8 to V10 sidedress N was applied at rates of 45, 90 and 134 kg N ha^-1 at variable distance of 0, 10, 20 and 30 cm from the corn row. The middle corn rows were harvested at maturity and data statistically analyzed using SAS package. The results indicated that, of all the studied sites, corn yields significantly (p<0.05) decreased with increased application distance. However, across sites and season, corn yields were variable ranging from 949 to 7601 kg ha^-1, and increased with applied N. Overall, application distance did not contribute to corn yield differences apart from the Efaw site, although positive N response was generally observed.

Keywords: Nitrogen placement, corn grain yield, nitrogen use efficiency