A NONLINEAR MODEL FOR CROP DEVELOPMENT AS A FUNCTION OF TEMPERATURE

The Beta function, commonly used as a skewed probability density function in statistics, was introduced to describe the effect of temperature on the rate of crop development. The framework is set by three cardinal temperatures, namely the base (T-b), the optimum (T-o) and the ceiling (T-c) temperature, The model parameters T-b and T-c and three other coefficients mu, alpha and beta can be used to derive;the value of T-o and the maximum development rate, Parameter alpha also characterizes the curvature of the relationship with temperatures between T-b and T-o, and parameter beta describes the curvature between T-o and T-c. The model has one parameter less than the Rice Clock Model (RCM); and in contrast to the RCM, it ensures that the maximum-development rate occurs exactly at T-o. The model accurately described the response to temperature of several developmental processes, and was superior to two widely used thermal time approaches in predicting rice flowering time.