| dc.description.abstract | 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. | |
