A Nonpoint Source Model for Land Areas Receiving Animal Wastes: I. Mineralization of Organic Nitrogen

Abstract

ABSTRACT A simple model based on current state-of-the-art was developed to describe the nitrate accumulation in land areas receiving animal wastes or plant residues. Earlier models using decay series were useful in predict-ing long term mineralization, but are less precise in determining the actual rate of mineralization or are less useful in transferring to other wastes which have not been studied. Utilizing the waste characteristics (C/N) and the soil nitrogen content, the model developed can be used to estimate the total potentially mineraliz-able N after the application of a waste to soil. This value is an asymptotic inorganic N yield achieved over the long term. Assuming a first-order kinetics for mineraliza-tion, the rate constants based on available literature were developed. It was concluded that about 50 percent of the N available for mineralization was converted in 3 to 6 wk for poultry and swine wastes. In comparison, beef wastes required approximately 18 wk under similar conditions. For wastes with C/N greater than 23 a lag period occurs as carbon is metabolized and lost, after which mineralization occurs with a rate constant of about 0.0077/day (at 35 C). Correction factors were developed for the major soil and environmental parame-ters affecting the mineralization rate. These factors were soil temperature, soil moisture, soil pH, and method of application of the waste.