Modeling the productivity of agricultural crops in response to water and nitrogen availability

Interception of photosynthetical active radiation, water and nitrogen uptake are the most important processes governing crop growth and production. Each of these processes is handled in a general way, and based on experimental evidence the main features are depicted. Light interception by a crop canopy determines the potential growth rate, provided the water and nitrogen uptake rates are optimal. Reasons for yield reductions in response to water and nitrogen shortage are clarified. During the growing period, the availability of growth factors can vary widely. Dynamic simulation models are a valuable tool in studying the quantitative aspects of crop growth processes. The way in which potential growth processes are modeled is presented. As water and nitrogen shortages put restrictions on the potential growth, these effects are modeled by their impact on relevant physiological processes. Finally, attention is paid to the practical use of simulation models with respect to agricultural crop productivity.