Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 8/15/1995
Publication Date: N/A
Technical Abstract: The soil's contribution of N is an important factor affecting the amount of supplemental N needed for optimum crop production. Our objectives were to quantify N mineralization of soils of Nebraska's Central Platte Valley and to use this information to improve current N recommendations. Corn N response trials were conducted at 23 irrigated sites (1991-1994) representing the regional soils distribution. Soils were incubated at 25C for 18 wk and thermal units were used for linking laboratory and field conditions. Optimum N rates varied from 0 to 264 kg/ha irrespective of grain yields (avg. = 11.0 Mg/ha). Mineralization of soils at max. N uptake varied 126 kg N/ha, but high residual soil NO3-N precluded calibration analysis against plant N uptake. Instead, we used an integrated approach that related optimum N rates and combined N sources. A spline function using only residual NO3-N (R2=0.69) showed that this test was very effective for identifying non-responsive sites; average prediction error for responsive sites was 51 kg N/ha. Adding N mineralization improved prediction of N needs (R2=0.87) and reduced this error to 30 kg N/ha. Alternatively, soil organic matter or total N tests can be used with similar success based on calibrated factors developed from mineralization data obtained in this study.