[A mathematical model of water stress and light condition effects on cotton dry matter and yield formation]

A mathematical model was developed to analyze the effects of water stress and light condition on crop dry matter accumulation and yield formation based on canopy carbon net assimilation rate. The function leaf water potential (psi l) indicating the water status of canopy was incorporated into this model, according to the assumption that the canopy resistance (Rc) was increased under the conditions of water stress and low light density. Psi l was estimated by a simplified regression equation, in which, the independent variables were relative soil moisture (Aw), ambient temperature (Ta), and vapor pressure deficit (VPD). The aerodynamic resistance (Ra) in the model was defined as a function of wind speed (u), and the yield was calculated by a linear increase in harvest index (hi) with time. The modeled data agreed well with the data observed from pot experiment. Sensitivity analysis and simulation results suggested that the model could be useful in identifying environment factors, especially soil water content and light density effects on crop growth and yield formation.