Dynamic model of the response of a vegetative grass crop to light, temperature and nitrogen

Abstract A previously described growth model of the vegetative grass crop is extended to include a simple representation of the root system, uptake of nitrogen from a soil nitrogen pool, and response to fertilizer application. The model simulates the processes of light interception, photosynthesis, partitioning of new growth, leaf area expansion, growth and maintenance respiration, ageing of plant tissues, senescence, recycling of substrates from senescing tissues, nitrogen uptake by the plant, leaching, mineralization, and fertilizer application. A principal component of the model, nitrogen uptake, is assumed to depend positively on plant carbon substrate concentration and soil nitrogen concentration, and to be inhibited by plant nitrogen substrate concentration. The dynamic responses to different levels of soil nitrogen, of shoot and root growth, nitrogen uptake and root activity, carbon and nitrogen plant substrate concentrations, and the fraction of substrate carbon used by the shoots, are examined; realistic behaviour is observed. The model predicts nitrogen fertilizer responses of yield and plant nitrogen content, which are compared directly with experimental data; good agreement is obtained.