Optimum Preplant Nitrogen Rates in Winter Wheat (Triticum Aestivum L.) And Maize (Zea Mays L.)

The optimum amount of preplant nitrogen (N) for winter wheat changes from year to year and depends greatly on the production environment in which it is grown. Optimizing mid-season N rates is possible using normalized difference vegetation index (NDVI) sensor based methods. The objective of this experiment was to determine the minimum amount of preplant N in wheat accompanied by N applied mid-season for maximum yields and increased nitrogen use efficiency (NUE). Four field experiments were conducted where N as urea ammonium nitrate (UAN, 28-0-0, N-P-K) was applied preplant at rates of 0, 17, 34, 51, 67, and 101 kg N ha-1. Preplant fertilizer was applied on October 6 for the Perkins and Hennessey locations, and October 8 and 9 for Lahoma and Lake Carl Blackwell, respectively. Normalized difference vegetative index data was was collected from the Feekes 3 growth stage and continued to the Feekes 7 growth (Large, 1954). At Feekes 5 growth stage, topdress N was applied at rates of 34 kg N ha-1 and 67 kg N ha-1. . The optimum preplant N rate for these studies was 67 kg N ha-1 (Tables 7, 8, 9, 10). In order to maximize yields, at least 34 kg N ha-1 applied topdress was needed. Abstract (maize):Overuse of nitrogen (N) fertilizer for maize production is prevalent. Optimizing mid-season N rates are possible using normalized difference vegetation index (NDVI) sensor based methods. The objective of this experiment was to determine the minimum amount of preplant N in maize accompanied by N applied mid-season for maximum yields and increased nitrogen use efficiency (NUE). Two maize trials were conducted where N as urea ammonium nitrate (UAN, 28-0-0, N-P-K) was applied preplant at rates 0, 17, 34, 67, 101, 134, and 168 kg N ha-1. Preplant fertilizer was applied within four days prior to planting at both locations. Normalized vegetative index data was collected at the V5, V6 and V9 growth stages.. Mid-season sidedress fertilizer N application was applied at the V-6 growth stage at a rate of 168 kg N ha-1. . This research should assist in recognizing the growth stage when maize plants will visibly show a deficiency. Due to environmental anomalies encountered, this maize N study will be conducted in the 2016 growing season. This work should determine the minimum preplant N rate needed combined with sidedress N for maximum yields in maize.Plant & Soil Science