Submitted to: World Fertilizer Congress of International Scientific Centre of Fertilizers
Publication Type: Abstract only
Publication Acceptance Date: 9/13/1997
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Prediction of naturally produced nitrate-N aids efficient use of N-fertilizer. A N-fertilizer aid has been developed which relies on 3 variable factors, temperature, rainfall, and soil bulk density and 3 nearly constant soil factors, clay content, pH, and organic matter content. Single-variable functions describe soil water content, temperature, and pH effects on nitrate-N formation. Redistribution of nitrate in the 0 to 60-cm depth is a function of daily water balance. Trials of the decision aid were conducted on 5 regional farms. Farmers conducted normal tillage, fertilization, and planting practices but left 6 to 12 rows of maize without added N. The prediction aid was initialized with soil characteristics and soil nitrate-N concentrations at planting time. Climatic data were used to predict nitrate-N in a 0 to 60-cm profile at the th-leaf stage of growth. Soil samples were taken immediately before fertilizer application and later analyzed for nitrate-N. Change in nitrate-N between the two samplings ranged from -6.4 to 11.7 ug/g with a mean of 2.52 +/- 4.18 ug/g. The predicted change in nitrate-N ranged from -0.25 to 10.7 with a mean of 2.31 +/- 2.14 ug/g. Grain yields were obtained at harvest from 30-m lengths of row and analyzed for treatment effects. Using the decision aid, the same yields were obtained usually with less applied fertilizer N. The median Aid:Producer grain yield ratio was 1.04.