A model for the simulation of the fate of nitrogen in farm wastes on land application

Abstract

SummaryA model for predicting the various transformations undergone in the soil by nitrogen applied in farm wastes, in response to variations in soil and climatic factors, is presented. The soil is divided into layers and a simple mass balance model is used to describe the movement and redistribution of water within the soil profile, as a function of rainfall, evapotranspiration and soil moisture characteristics.Ammonification of native and applied organic N is assumed to follow first-order reaction kinetics and nitrification and denitrification are treated as zero-order reactions. The rates or rate constants for all three reactions were related separately to soil temperature, moisture content and pH.Uptake of nitrogen by a grass crop, dry-matter production, removal of dry matter and N through harvests, addition to soil of C and N through dead plant material and stubble and the consequent immobilization of mineral N are allowed for. Some of the predictions of the model are compared with the results of a lysimeter experiment.