Precision Regulation Model of Water and Fertilizer for Alfalfa Based on Agriculture Cyber-Physical System

The regulation of water and fertilizer for alfalfa growth is not precise enough because the regulation strategy cannot track alfalfa growth dynamically. In this paper, we propose a precision regulation model of water and fertilizer for alfalfa based on agriculture cyber-physical system (ACPS) for irrigation and fertilizer management in alfalfa (PRMWFA-ACPS). The proposed PRMWFA-ACPS is a comprehensive model that includes the biophysical submodel, the computation submodel of water and fertilizer regulation, and the interaction of the submodels for both. The proposed model interacts with the alfalfa growth and its physical environment along with the irrigation strategy to improve the precise regulation of water and fertilizer. To verify the performance of the proposed model, we develop a simulation platform for PRMWFA-ACPS based on Ptolemy. Through physical experiments performed in the field at the Ningxia irrigation area of the Yellow River over three years (2016-2018), we verified and analyzed PRMWFA-ACPS by comparing the simulated and measured values, such as the growth period, leaf area index, soil water content and alfalfa yield. The experimental results show that the mean relative error of the growth period simulated by the model is between 1.9% and 6.8%, the mean relative error of the leaf area index simulated by the model is between 2.1% and 9.8%, the mean relative error of the soil water content simulated by the model is between 4.3% and 12.8%, and the mean relative error of the yield simulated by the model is between 1.2% and 14.3%. These findings indicate that PRMWFA-ACPS has promising applicability to the Ningxia irrigation area of the Yellow River and improves the accurate regulation of water and fertilizer application to alfalfa in a complex physical environment.