Coupled Characterization And Synergistic Regulation Of Agricultural Water-energy-food Nexus Systems Under Changing Environments

The structural adjustment of agricultural water resources use and land resources is closely related to the water-energy-food nexus system,and the study on the synergistic regulation of agricultural water and land resources coupled with the water-energy-food nexus system is important to clarify the key processes of regulation and their synergistic relationships,which is a new perspective of agricultural water and land resources management.Meanwhile,agricultural water,energy and food resources are significantly influenced by the changing environment.Therefore,the synergistic relationship between water-soil-energy-food,the volatility of water supply,the dynamic water cycle process and the synergistic regulation of multi-energy objectives in a system under the changing environment are worthy of further investigation.Based on the quantitative characterization of the agricultural water-energy-grain nexus system,this study constructs a water-soil resource optimization and control model based on the water-energy-grain nexus in a changing environment at the farm scale and irrigation district scale,respectively,using the Acheng experimental base of Northeastern Agricultural University and the Jinxi irrigation district in Heilongjiang Province as the study area,and obtains optimal water,soil,and energy resource regulation schemes for future agricultural water,energy,and food resource management under changing conditions,Energy and food resources sustainable management in agriculture under changing conditions.The main research contents and conclusions are as follows:（1）At the farm scale,the experimental base in Acheng,Northeast Agricultural University,Heilongjiang Province,was used as the research area.（1）At the farm scale,nine groups of trials and one control group were conducted at the experimental site of Northeastern Agricultural University in Acheng,Heilongjiang Province,with three fertilizer concentrations（F1-600 kg/hm²,F2-750 kg/hm²,F3-900 kg/hm²）and three biochar concentrations（B1-7500 kg/hm²,B2-11250kg/hm²,B3-15000 kg/hm²）in soybean.The field trials were conducted to investigate the effects of water,fertilizer and biochar on crop growth characteristics and soil environment.Based on the analysis of the field trial data and results in 2021,the daily trends and correlations between stomatal conductance and environmental parameters were revealed,with a positive trend of correlation between stomatal conductance and saturated water vapor pressure difference before 12:00 a.m.and a negative trend after 12:00 a.m.Stomatal conductance photosynthetic effective radiation and ambient temperature showed positive correlation trend overall.Stomatal conductance and ambient CO₂ concentration showed a positive trend from 12:00 to 14:00,and a negative trend in the rest of the time.The dynamic changes of soil water content at different fertility stages at different treatment levels were clarified,i.e.,the soil water content in June,July and August was higher than that in May and September,and the trend of soil water content was the same for different treatments,and the average yield of soybean could be obtained as 2286 kg/hm² by the results of water allocation at different fertility stages.the above study can quantify the farm-scale water-energy-grain nexus The above studies can quantify the changes in water,photosynthetic energy and respiratory energy from photosynthesis and respiratory flux of soil in the relationship between water,photosynthesis and respiration,and their effects on soybean grain yield.（2）Based on the water-energy-grain nexus at farm scale,a multi-objective nonlinear optimal allocation model of water resources with the synergistic enhancement of intrinsic water use efficiency,field water use efficiency,and ecosystem water use efficiency was established to investigate the quantitative form of water resources and the energy conversion process of crop growth involving photosynthesis and respiration at different scales.Based on the results of field experiments to fit the parameters of the coupled Javris model in the objective function of intrinsic water use efficiency,to obtain the potential soil water content and potential yield data of the coupled Jensen model in the field water productivity objective,and to obtain the soil respiration data of the ecosystem water productivity objective as the parameter inputs in the functional relationship of the optimization model,the affiliation function method was used to The model was solved,and the results of dynamic water allocation and synergistic satisfaction of intrinsic water efficiency,field water use efficiency,and ecosystem water use efficiency were obtained at different treatment levels,and relative to the CK control treatment,the intrinsic water use efficiency of the optimized medium concentration of compound fertilizer and medium concentration of biochar F2B2 treatment increased by 26.22%,field water productivity increased by 35.68%,ecosystem water use efficiency by 15.05%,and satisfaction by 34.49%,and the overall trend of water allocation throughout the reproductive period was consistent with that of the CK group,with the F2B2 treatments having water allocation percentages of[11.28%±0.61%],[22.58%±1.76%],[25.32%±1.56%],[26.75%±1.78%]and[14.23%±2.16%],while the average yield of optimized soybean can be obtained as2548 kg/hm²,which is 11.46%higher than the actual yield.On this basis,eight climate change scenarios were identified based on the CMIP6 program to explore the changes in water allocation and each water use efficiency for 2021-2040 under different climate models,and the results showed that the highest water allocation per unit area was 978.12 m³/hm² under the SSP5-8.5＿2021-2030scenario.for the SSP1-2.6＿2031-2040 scenario,the intrinsic water use efficiency increased by3.31%,field water productivity increased by 2.98%,ecosystem water use increased by 1.73%,and the synergistic satisfaction of the three objectives increased by 5.26%.The optimization model established above can effectively quantify the water allocation relationships and the synergistic effects of linked intrinsic water efficiency,field water use efficiency,and ecosystem water use efficiency multi-water use efficiency during soybean growth,and provide a method for the synergistic regulation of farm-scale water-energy-grain nexus systems.（3）At the regional scale,an optimization modeling method based on multi-objective nonlinear programming,left-right type fuzzy numbers and uncertainty with confidence constraints is proposed to optimally regulate water resources,cropping structure and energy resources from the perspective of synergistic multienergy of light,electricity and biomass energy considering water cycle processes.The method aims to assess the interactions and synergistic relationships among biomass electrical energy,light electrical energy and hydroelectric energy,to elucidate the dynamic characteristics of resource allocation and socio-economic and environmental impacts,and to capture the high uncertainties in the associated fields.The method was applied to the Jinxi Irrigation District in Heilongjiang Province.The results show that there are trade-offs and games among light energy utilization,hydroelectric energy and biomass electric energy,and their coordination leads to a 12.22%increase in system synergy between resources,economy and environment,including a 2.67%increase in irrigation water use efficiency and a 4.92%increase in energy use efficiency.Water cycle processes and the uncertainties associated with model parameters and constraints significantly affect the synergy between multiple energy sources.More water will promote synergistic management of energy sources,and the degree of synergistic development will increase by 2.20%when the water volume increases by 4.16%,however,it is accompanied by a higher risk of water scarcity.The methodology contributes to the efficient and sustainable management of agricultural water,energy and land resources.The developed model for optimal regulation of agricultural water-energy-food nexus systems at different scales contributes to the sustainable management of agricultural water,land resources and energy,which in turn promotes food production.It also explores the dynamic effects of synergistic regulation of agricultural resources on water use efficiency,food production,economy,society,and environment under changing environments.The model developed in this study can be applied to other agricultural production regions,which is important for decision makers to improve agricultural development and promote sustainable agricultural development.