Tuesday, November 14, 2006 - 9:30 AM

Adjusting Mid-Season Nitrogen Using a Sensor-Based Optimization Algorithm to Increase Use Efficiency in Corn (Zea mays L.).

Brenda S. Tubana, Roger Teal, Brian Arnall, Kyle Freeman, Byungkyun Chung, Olga Walsh, Kyle Lawles, Clint Mack, and William Raun. Oklahoma State University, Ag Hall, Stillwater, OK 74078

Successful use of sensor based nitrogen (N) rate recommendations has resulted in an increase in N use efficiency (NUE) in winter wheat production. Due to increasing N fertilizer costs, development of a functional algorithm to optimize N fertilization in corn production is also essential. This study was conducted to formulate the in-season N optimization fertilizer algorithm (NFOA) that will be used to estimate the mid-season N rate requirement to maximize corn growth and minimize inputs.  In addition, the optimum resolution to treat spatial variability for NFOA-based sidedress N rates was determined. The experiment was established at three locations in 2004 (Efaw, Perkins and LCB) near Stillwater, OK consisting of 13 treatments arranged in a randomized block design (RCBD) with 3 replications.  Treatments consisted of three application methods: split application with preplant rates at 0 and 67 kg ha-1 and sidedress rates at 67 kg ha-1 or NFOA-based variable rates, preplant and sidedress only at 0, 67 and 134 kg ha-1.  In addition, one NFOA-based N rate was tested at 0.34 and 2.32 m2 application resolutions. Generally, higher grain yield (17% at Efaw in 2005) was obtained in plots with pre-plant N and mid-season NFOA-based N rates. High NUE values were obtained from plots without pre-plant N but applied with NFOA derived mid-season N rates.  While the NFOA employed increased grain yield for selected sites, NUE was consistently improved across site-years. Improved NUE was attributed to lower N inputs determined by the algorithm which is based on estimated yield potential.