In fact, the Soil Moisture Model is often referred to as the soil moisture balance equation, which is the basis of the model. A more effective and comprehensive model is introduced here. In order to determine the time and intensity of water stress, the soil water model considers the crop root density in the root layer, and simulates the corresponding changes of soil water content through the daily changes of root density to estimate the crop water stress index. Evaluation of plant water consumption based on crop root system in soil. Estimating plant water deficit index (PWDI) is widely used in production practice. The basic principle is that when the soil moisture in the root zone is at a certain suitable level, the crops are not stressed, that is, the root system has the highest water absorption rate and the strongest transpiration (potential transpiration); Otherwise, crops will be subjected to a certain degree of water stress, that is, the root water absorption rate and transpiration intensity will decrease. According to the engine model, the relative crop root density is used as the weighting factor to calculate the soil water matrix potential of each soil layer in the root zone, and the weighted average soil water matrix potential of the root zone is used to estimate PWDI.
The engine replaces the root density in the traditional calculation with the corresponding density of the relative root layer, thus improving the PWDI estimation method and applying it to optimize the irrigation and fertilization system. This method is the core soil moisture model in the irrigation and fertilization decision engine.