Submitted to: Minnesota Academy of Science Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 4/29/1995
Publication Date: N/A
Technical Abstract: Nitrate-nitrogen concentrations in soils have been one of the most frustrating features to predict. Nitrogen, the major limiting element in most crop production, is necessary for sustained food and fiber production. However, the excess amounts of fertilizer-N applied to the soil are a source of Nitrate-nitrogen pollution to ground water and represent a waste to crop producers. Therefore, a need exists for accurate prediction of the amount of nitrogen fertilizer needed for optimal crop yield. Soils have a natural potential to produce Nitrate- nitrogen, and this potential is affected by the aeration of the soil. A model has been developed to determine the coefficient of aeration for Nitrate-nitrogen production by soil microorganisms. The model uses 5 primary components or soil characteristics; these are clay content, temperature, water content, pH, and bulk density. Each component is defined by a mathematical function using a principle of potentials. The hydrogen ion effect is described by a complex sech**2(pH) function. Soil water, bulk density, and temperature are described by complex tanh(x) functions. Clay content is as a simple variable. The program calculates a value for each component and integrates the various factors into a coefficient of soil aeration. Soil Nitrate-nitrogen can be estimated multiplying the aeration coefficient by the soil nitrogen mineralization potential. The program was written using the language C; this allows easy access to auxiliary computer files/data bases and incorporation of the program into other software developments such as FARMBOOK. Tests of the model using a variety of soils produce results which are consistent with field observation.