覆盖与施氮交互作用下黄土旱塬春玉米水氮高效利用机理及增产减排模式研究

To meet the demand of developing eco-efficient agriculture in China, it has become the focus of current research to alleviate the environmental pollution in agricultural production while ensuring high yield, water and nitrogen use efficiency in dryland farming. The drylands of northwest Loess Plateau of China is characterized by low precipitation utilization efficiency, excess nitrogen fertilization and aggravation of ecological environment. This project takes the main food crop of spring maize as a research object, and the synchronous development of high yield, high efficiency and low emission as a research objective. Through field experiments and numerical simulations with the DNDC model, we explore the mechanism of high-efficient water and nitrogen utilization by spring maize in drylands of Loess Plateau under interaction of soil mulching and nitrogen fertilization; study the interactive effects of soil mulching and nitrogen fertilization on soil pollution (nitrate accumulation and leaching) and atmospheric pollution (ammonia volatilization and greenhouse gas emission); develop comprehensive evaluation model by considering the agronomic, economic and environmental effects simultaneously; and propose an apposite soil mulching and nitrogen fertilization mode that ensures both high spring maize yield and low glasshouse gas emission. The results are aimed to provide a scientific basis for the high-yield cultivation of spring maize, agro-ecological environment protection and sustainable agriculture development in the drylands of Loess Plateau.

面向我国发展高效生态农业的需求，通过发挥覆盖与施氮的协同交互作用，调控旱作农田土壤水分和氮肥供应，在保证作物高产、水氮利用效率提高的同时，减少农业生产带来的环境污染威胁已成为当前研究的重点。本项目针对西北黄土高原旱作农业区降水利用率低、氮肥增施过量和生态环境恶化的现状，以当地主要粮食作物—春玉米为研究对象，以高产、高效、减排同步发展为目标，结合田间定位试验和DNDC模型模拟分析，揭示不同覆盖与施氮模式及其交互作用下旱作春玉米农田水氮高效利用机理；探明土壤环境污染（土壤硝态氮残留和淋溶）和大气环境污染（氨挥发和温室气体排放）对覆盖与施氮互作效应的响应机制；构建不同覆盖和施氮模式下同时考虑农学效益、经济效益和环境效益的综合效益评价模型；提出黄土旱塬春玉米增产增收与农田减排的适宜覆盖与施氮种植管理模式。为黄土高原旱作春玉米高效栽培、农业生态环境保护和农业可持续发展提供科学依据。

针对我国西北黄土旱塬降水利用率低、氮肥增施过量和生态环境恶化的现状，以旱作玉米为研究对象，以高产、高效、减排同步发展为目标，结合大田试验和DNDC模型，揭示了不同覆盖措施与施氮模式及其交互作用下旱作玉米水氮高效利用机理，探明了土壤环境污染和大气环境污染对覆盖与施氮互作效应的响应机制，构建了不同覆盖和施氮模式下同时考虑农学效益、经济效益和环境效益的综合效益评价模型，提出了旱作玉米增产增收与农田减排的适宜覆盖与施氮种植管理模式。研究结果发现，覆盖措施显著影响土壤温度，秸秆覆盖（SM）土壤温度最低，垄膜沟播（RP）土壤温度最高；SM和RP对玉米生育前期土壤水分有较好的保蓄作用；施氮模式对土壤温度和贮水量无显著影响。覆盖有利于提高玉米生长和生理特性，但SM和RP差异不显著；施氮量增加和高效氮肥施用显著促进玉米生长和生理特性。RP+U3（300 kg N/ha）平均玉米产量最高（9183.2 kg/ha），但U2（200 kg N/ha）处理下秸秆覆盖+尿素配施硝化抑制剂（SM+DMPP）产量与其无显著差异。SM（1141.6 USD/ha）与RP（1253.9 USD/ha）净收益无显著差异；随施氮量增加净收益增幅减小，尿素配施硝化抑制剂（U+DMPP）净收益高于其他施氮类型。施氮量增加硝态氮和铵态氮残留显著增加，U+DMPP显著降低土壤硝态氮残留，尿素配施脲酶抑制剂（U+NBPT）显著降低土壤铵态氮残留。覆盖措施对NH3挥发和CH4排放无显著影响，RP显著增加CO2排放，SM和NM处理CO2排放无显著差异；SM降低N2O排放，RP增加N2O排放，RP显著增加全球增温潜势（GWP）和温室气体强度（GHGI）（45.0%和29.8%），SM显著降低GWP和GHGI（22.2%和27.8%）；随施氮量增加N2O排放显著增加，U+NBPT显著降低NH3挥发，U+DMPP显著降低N2O排放；U+DMPP处理GWP和GHGI最小。DNDC模型能够较为准确地模拟不同覆盖措施下玉米产量，N2O排放模拟精度较低但模拟结果变化趋势与实测一致。基于组合赋权的TOPSIS模型分析可得，秸秆覆盖+200 kg N/ha+尿素配施硝化抑制剂能实现玉米产量、经济和环境综合效益最优。研究成果可为黄土高原旱作玉米高效栽培、农业生态环境保护和农业可持续发展提供科学依据。