CRISP (crayfish and rice integrated system of production): 1. Modelling rice (Oryza sativa) growth and production

A ecological sub-model for rice growth, adapted to the culture processes used in the lower Mondego river valley (Portugal), is presented. The structure of the model is based on the production of carbohydrates by the photosynthesis. Parallel structures were used to simulate the development stage of the crop, and the tillering process. The model is composed of 11 state variables, 14 forcing functions, 22 rate processes, 9 parameters and 17 switches, regulatory processes and calculated values. Simulations were performed for periods ranging from January 1995 to October 1996. During this period the simulation results were compared with data on aerial rice biomass and also on the tiller density. In addition, the simulated final rice production parameters were compared with the observed values for both years. It can be stated that the model performs well in what regards prediction of final production parameters but it underestimated rice biomass during the growth period. Although at this stage the model is mainly directed towards research, the final purpose is the management of crayfish and rice production. In order to achieve this aim, it will be necessary to couple several sub-models.