| Food security,climate change,water shortages,environmental pollution,and other significant issues pose a threat to agricultural output.A fundamental requirement for the development of sustainable agriculture is the efficient use of soil and water resources.However,there is a problem with the inefficient comprehensive use of agricultural soil and water resources,so it is important to research the synergistic deployment of agricultural soil and water resources with synergistic enhancement of water conservation-emission reduction-efficiency.This study uses Heilongjiang Province as its research area,combines field experiments and optimization modeling,and divides the region’s irrigation cropping system into three levels:farmland maize cropping system,farmland soybean cropping system,and regional irrigation cropping system to reveal the impact law of agricultural water and soil resources utilization and fertilizer,straw,and biochar application on crop yield and greenhouse gas emission.Based on the synergy of yield,water and nitrogen consumption efficiency,and water and carbon footprint,the optimal control models of water,nitrogen,biochar,and straw for maize,nitrogen,biochar,and irrigation water for soybeans,and the optimal control models of planting structure.The best models for controlling water,nitrogen,biochar,and straw for maize based on synergistic multi-dimensional goals of yield,net economic efficiency,and net carbon emission;the best models for controlling nitrogen fertilizer,biochar,and irrigation water for soybean based on synergistic multi-dimensional goals of yield,water and nitrogen utilization efficiency,crop water,and carbon footprint;and the best models for controlling planting.By balancing the conflicts between several objectives of efficient use of water and soil resources,economic efficiency,and environmental effects,the study seeks to give methodological support for the sustainable and coordinated use of agricultural resources.The following are the primary findings and research recommendations:(1)On-farm maize planting system:Using the modern agricultural high-tech demonstration park in Harbin,Heilongjiang Province as the research area,we propose a method that integrates experiments and optimization models,and design three kinds of nitrogen application concentrations,three kinds of biochar application concentrations and three straw application concentrations,and combine the composition to generate nine groups of orthogonal tests and a control group of field trials to find the best water,nitrogen,biochar and straw utilization patterns The study aims to achieve synergy between economic and environmental aspects of maize.The response functions of carbon emissions between maize yield and fertilizer,water,biochar and straw use were simulated.A multi-objective nonlinear model was developed to balance the economic and environmental effects of combined fertilizer,water,biochar and straw use.The results showed that the N-water-biochar-straw use model with 275 kg/hm~2-175 mm-9800 kg/hm~2-4210 kg/hm~2 the greatest coordinated development of yield-net profit-net carbon emission,and the degree of coordination of the optimized model improved by 22.25%over the optimal field trial treatment and by 58.24%over the CK condition.The optimal economic benefit per unit of net carbon emissions improved by 8.21%over the experiment,balancing the trade-off between economic benefits and carbon emissions.This study contributes to the sustainable use of soil and water resources in maize cultivation.(2)On-farm soybean cropping system:The experimental site of Northeastern Agricultural University in Acheng,Heilongjiang Province,was used as the study area.three species of nitrogen application concentrations and three species of biochar application concentrations were combined to generate nine experimental groups and a control group in a field experiment to construct an optimal regulation model of soybean nitrogen fertilizer,biochar and water quantity based on the synergistic multi-dimensional objectives of yield,water and nitrogen utilization efficiency,crop water footprint and carbon footprint,and to investigate the synergistic effects of nitrogen fertilizer,biochar application and irrigation water quantity on yield and environmental effects.The results showed that the N1B2 treatment had a high yield and environmental impact.The results showed that N1B2 treatment had the highest soil water content,N3B3 treatment had the highest soil carbon sequestration,and N2B2 treatment had the highest yield.The optimal synergy among the multidimensional objectives of soybean life cycle water footprint,carbon footprint,water use efficiency,nitrogen and fertilizer bias productivity,and yield could be achieved when the nitrogen fertilizer application was 280 kg/hm~2,biochar addition was 7600 kg/hm~2,and irrigation water was170 mm(when the precipitation was less than 408 mm),and the coordination degree reached 0.9,and the synergistic regulation of water,nitrogen,and biochar reached a high-quality coordination level.The optimized results compared with the optimal test treatment N2B2 showed that soybean yield increased by 2.62%,water footprint decreased by 8.85%,carbon footprint decreased by15.79%,water use efficiency increased by 18.32%,and nitrogen fertilizer bi-productivity increased by 9.97%.This study contributes to the sustainable use of soil and water resources in soybean cultivation.(3)Regional irrigation planting system:Taking planting as the research object,182 typical irrigation areas in Heilongjiang Province are used as the research area.A multi-dimensional synergistic optimization modeling method of planting structure based on system dynamics is constructed.With the goal of maximizing the synergistic development of five dimensions of regional water resources,society,economy,ecology and environment,the systematic association and dynamic evolution law of each dimensional driving element is simulated based on the system dynamics method,which is coupled into a multi-dimensional multi-objective planning model to achieve multi-dimensional optimization and dynamic prediction of planting structures in different regions.The results show that compared with the status quo(2016),the optimized planting structure in 2016,2025 and 2030 increases the degree of synergistic development of resource,economic,social,environmental and ecological multi-dimensional complex systems by 24.14%,42.36%and51.36%,respectively,and shows a trend of annual growth,and through the optimization of planting structure,the degree of synergistic development of the agricultural system in Heilongjiang Province increases from barely coordinated state to a high-quality coordinated state,promoting sustainable agricultural development.There is a significant improvement in resource utilization efficiency in northern and western Heilongjiang Province,which is more than 25.36%;a significant improvement in economic efficiency in central Hehe,Yichun and Suihua beyond the junction of Sodu,which is more than 27.25%;and a reduction in environmental pollution in western,southern,northern Daxinganling and Jixi,which is more than 25.65%.This study contributes to the sustainable use of soil and water resources in irrigation area cultivation. |
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