Abstract
A dynamic crop growth model was developed to analyse irrigated paddy rice (Oryza saliva L.) productivity as determined by climatic factors and N availability. The model consists of submodels related to soil N processes, rice N-uptake, developmental processes, photosynthesis, dry matter production and spikelet formation. Soil N processes include N mineralization, expressed as a function of temperature and soil moisture before flooding. The balance between soil N supply and crop N demand determines rice N-uptake. The phenological developmental rate was expressed as a non-linear function of daily temperature and daylength. Submodels for canopy photosynthesis and dry matter production were based on an age-dependent relation between single-leaf photosynthesis and leaf N. Spikelet number was determined by an empirical function of dry weight and N concentration of above-ground biomass at the panicle formation stage, which was derived from a number of field experiments conducted in widely different regions in Japan. Data sets covering a range of N and climatic conditions were used for validation. The model, written in BASIC for PCs, satisfactorily simulated daily biomass growth and final spikelet number with inputs of latitude, N fertilizer input and daily climatological data, and might be useful for evaluation of N fertilizer management scenarios over sites and seasons.
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