Simulating nitrogen response of irrigated rice

A dynamic model to simulate the growth and yield of irrigated, transplanted rice in relation to daily solar radiation, mean temperature and shoot nitrogen concentration was applied to rice crops in western Java, Indonesia. Observations of shoot nitrogen concentration throughout the life-cycles of experimental crops were used as input to the simulation. The experiments consisted of 23 treatments representing different forms of nitrogen fertilizer, and different rates, times and methods of application. The model accurately fitted the growth and yield of 12 of these treatments and was successfully tested on the 11 treatments which were not involved in the fitting. The parts of the model dealing with nitrogen simulate daily growth as a non-linear function of nitrogen concentration of non-grain shoot tissue relative to upper and lower limits. During the grain-filling phase the model simulates the competition for plant nitrogen between grain and assimilating tissue. The model was used to simulate the effects of increases in nitrogen status of a rice crop in the environmental conditions of western Java. Simulations with the model suggest an interaction between the timing and amount of nitrogen accumulation in plant tissue, with little effect of timing on yield for small increases in nitrogen status, but an advantage for early over late application for large increases in nitrogen status.