Nitrogen modeling for soil management

ABSTRACT:

Simulation models of the nitrogen (N) cycle have been used for well over 20 years to help estimate nitrate (NO₃-N) leaching, soil residual NO₃-N, fertilizer N requirements, soil organic N status, and gaseous N emissions associated with agriculture. These models have been coupled with simulations of other related processes such as water and solute transport, crop growth, soil chemistry, temperature regimes, and management to make more complete models of cropping systems. At the core of these tools have been databases for soils, climate, model coefficients, and field/farm/watershed management scenarios. This paper reviews the basic types of N modeis, modeling techniques, and required databases. The accuracy of N models along with their strengths and limitations are discussed in a management context. Tips are provided on initializing N constituent pools, on using N models in Geographic Information Systems (GIS) applications, on developing confidence bands for N model output, and on using web-based N models. Finally, methods are described to analyze simulated NO₃-N leached, nitrous oxide (N₂O) emissions, and N use efficiencies.