Research On Precision Regulation Technology Of Water And Nitrogen For Alfalfa Based On Agriculture Cyber-Physical System In The Ningxia Irrigation Area Of The Yellow River

With the agricultural structure adjustment in northwest China,it is important to use advanced computer technology to realize the coordinated regulation and management of climate,alfalfa and environmental resources in the complex physical environment.Previous studies focus on the physical environment construction associated with objects.The attention towards the dynamics of crop growth and the feedback of physical environment is not enough in precision regulation,thus affecting the accuracy of regulation strategy.The agriculture cyber-physical system(ACPS)is the cyber-physical system(CPS)as applied to agriculture.It describes the physical world through modeling and enhances the regulation ability of agricultural systems through the deeper integration and interaction of computation with physical environment.The alfalfa growth process is a continuous biological process,and changes in soil moisture and nitorgen are continuous physical processes.The water and nitrogen precision regulation strategy is performed by computer technology.It is a discrete computation process.The computation process and biophysical process interact continuously to improve the water and nitrogen regulation ability for alfalfa Therefore,the precision regulation of water and nitrogen in alfalfa is a specific application of ACPS.The comptation and biophysical fusion method of ACPS provides a way to improve this problem This is crucial for the effective allocation and optimization of agricultural resources in the Ningxia irrigation area of the Yellow River.The precision regulation of water and nitrogen for alfalfa based on ACPS is an agent with deep integration of physical and computation.In the regulation process,the challenges are how to obtain the growth dynamics of alfalfa under different irrigation methods and different water and nitrogen conditions,how to integrate the alfalfa growth model into ACPS and design the regulation algorithm of water and nitrogen to realize the interaction and integration with the biophysical processes,and how to build the ACPS precision regulation information platform to achieve dynamic strategy formulation and prediction.To address these three issues,we deeply analyzed the alfalfa growth model and the basic theory and operation mode of ACPS.We adopt the method of combining modeling and field experiment to study the key technology of alfalfa in precision regulation of water and nitrogen.The main conclusions are as follows:(1)An alfalfa growth simulation model based on water and nitrogen factors(ALFSIM-WN)was proposed.The model was divided into crop dynamic sub-model,water balance sub-model and nitrogen balance sub-model.It could estimate the yield of alfalfa under different water supply and variable fertilization.We performed physical experiments performed in the field at the Ningxia irrigation area of the Yellow River in 2016-2017.The results show that the growth period simulated by the model is consistent with the growth period of local forage harvesting purpose.The mean relative error of the leaf area index,the soil water content and the yield simulated by the model are 2.3%?17.6%,2.3%?17.6%and 1.7%?16.2%,respectively.The root mean square error are 0.09?0.44,0.009?0.039 cm3/cm3 and 0.3?2.3 t/hm2,respectively.These findings indicate that the ALFSIM-WN has higher simulation accuracy and good application in the Ningxia irrigation area of the Yellow River.(2)Based on the ACPS,firstly,a precision regulation architecture of forage based on ACPS(PRACPS)was proposed We analyzed the interaction among the physical space,the network space,the cyber space,manager and evaluation system.Secondly,we based on the PRACPS and proposed a precision regulation model of water and nitrogen for alfalfa based on ACPS(PRACPS-ALFA),which including the biophysical sub-model,the computation sub-model,and the interaction of the sub-models for both.Moreover,the computation sub-model comprehensively considers the environmental factors and future weather prediction to improve the accuracy of water and fertilizer irrigation management.A multi-factor water and nitrogen precision regulation algorithm based on predictive(MWFAP)was proposed,which could make precision regulation strategy of water and nitrogen and predicted the yields for alfalfa according to different external physical environment.Finally,the results of four consecutive field physical experiments in 2018 show that the mean relative error of the soil water content and the yield simulated by the model are 5.9%?12.8%and 1.2%?8.7%,respectively.The root mean square error are 0.018?0.037 cm3/cm3 and 61.2?639.3 kg/hm2,respectively.These findings show that the model has higher accuracy and better applicability in the Ningxia irrigation area of the Yellow River.It can realize the precison regulation of water and nitrogen for alfalfa in the complex physical environment.(3)Based on PRACPS-ALFA and Ptolemy,an ACPS alfalfa precision regulation information platform was built through the tree structure design method.It intergated the continuous system and discrete system.We used the platform to formulate the irrigation schedule and predict alfalfa yields in 2019,and compared this irrigation schedule with the actual quota irrigation schedule in the Ningxia irrigation area of the Yellow River The results show that the information platform can adjust and predict the irrigation amount of alfalfa in the growth period flexibly and accurately according to the alfalfa growth dyanmics,the external physical environment changes and the future rainfall.The water saving rate is 44%under the flood irrigation and 8%under the subsurface drip irrigation.The precision regulation strategy of water and nitrogen for alfalfa based on ACPS can be well used to achieve the precison regulation of alfalfa water and nitrogen under different meteorological conditions and different irrigation methods.The field experiment shows that the model has good effect in application.Moreover,the model has good scalability.By adjusting the parameters of the physical environment and algorithms,this model can realize the regulation strategy of alfalfa water and nitrogen in different regions and different production needs.This methods provides a reference for the precision regulation management and prediction of alfalfa in the western China.