Effect of Nitrogen Fertilizer Rate and Placement on Corn Grain Yield

Abstract

By-plant application of nitrogen (N) fertilizer has the potential to increase N use efficiency in corn (Zea mays L.). This study was conducted to evaluate the use of directed stream application at the base of the plant using UAN (urea ammonium nitrate) versus dribble surface bands applied in the middle of the row, and to evaluate the use of directed stream application by-plant using UAN versus dribble surface bands applied in the middle of the row. The experiment was conducted at the Robert L. Westerman Irrigated Research Station at Lake Carl Blackwell, OK (LCB), and at the Eastern Research Station at Haskell, OK for three years. The experimental design was a randomized complete block with three replicates. Treatments were three N placement methods and applied in three different methods; 1. stream at the base of the row; 2. by plant at the base of the plant; and 3. stream between the rows. Each treatment method had four N rates split applied, and three N rates applied all pre-plant. At the Irrigated LCB site, in 2005, 2006, and 2007 an increase in grain yields from by-plant N application at lower rates when compared to commonly applied N in the middle of the row. Similarly, at the non-irrigated site at Haskell, by-plant fertilization showed improved grain yields at lower N rates in 2005. At Haskell in 2006 the middle two N rates (90 and 135 kg N ha-1) resulted in slightly higher yields when fertilizing by-plant. In 4 of 6 site years , there was a slight advantage associated with applying N by-plant at lower N rates compared with N applied uniformly in the middle of the row. The benefits of fertilizing by-plant tended to be more evident when yields were lower and the production cycle was characterized by moisture stress.