旱作冬小麦-填闲作物系统土壤水碳氮过程及其对作物产量和温室气体排放的影响

Intergration of cover crop into annual crop rotations presents an opportunity to increase the ecosystem services as maintenace soil quality, increasing soil fertility and squenstration of soil organic carbon and reducing the greenhouse gas emissions. In this project, the dynamics of soil water, carbon/nitrogen pools, greenhouse gas (CO2、CH4、N2O) flux and crop biomass and yield are measured systemtically on both a winter wheat - summer cover crop rotation system and two incubation experiments with respect to precipitation simulation and cover crop residue decompositation. The effects of intergration of summer cover crop on soil water cycle and succeding crop water use will be clarified in face of precipitation changes in different years. The contributions of legume and non-legume cover crop to soil carbon/nitrogen pools and crop uptake will be compared. The responses of greenhouse gas emission and net global warming potential to summer cover crop growth and incorporationin will be investigated during the whole agricultural year. Also, with the perspectives of the soil water, carbon and nitrogen processses, the comprehensive ecological functions of crop producttion, carbon sequesteration and greenhouse gas emission reduction will be assessed for the dryland winter wheat –summer cover crop rotation system. The proposed results will give a scientific support for the establishment of such cropping system in the Northwest China.

将填闲作物引入作物种植系统具有改良土壤、提高肥力、固碳减排等多种生态效益。项目针对旱作冬小麦农田系统，依托田间定位试验、降水模拟土柱试验和填闲作物残余分解培养试验，通过对土壤水分、碳/氮库、温室气体（CO2、CH4、N2O）通量和作物产量的系统观测，分析不同降水年型填闲种植对农田土壤水分平衡和作物水分利用的影响规律，确定豆科和非豆科填闲作物对土壤碳/氮库和后续粮食作物养分利用的贡献，阐明填闲种植对农田温室气体排放的内在影响机制，揭示冬小麦-填闲作物系统温室气体排放规律和净综合增温潜势形成过程；并从土壤水碳氮过程和温室气体排放角度，对旱作农田冬小麦-填闲作物系统的稳产、固碳、减排效益加以综合评估，预期成果可为该系统在我国西北旱作农业区的建立与推广提供科学依据。

填闲种植具有改良土壤、提高肥力、固碳减排等多种生态效益。项目针对旱作冬小麦单作系统，依托田间定位试验、降水模拟盆栽试验、填闲作物残余腐解原位和培养试验，并结合文献分析方法，对填闲种植系统土壤水分、碳/氮组分、温室气体（CO2、CH4、N2O）通量和作物产量进行了系统观测研究。结果表明，①全球尺度上填闲种植总体上提高了作物蒸散量和水分利用效率，但对降水储存效率和粮食作物产量影响不大。提前终止填闲作物、将填闲作物翻压入土或地表覆盖以及延长填闲种植年限均能有利于旱作填闲种植系统作物产量形成和水分利用。②在黄土高原地区，种植长武怀豆和怀豆与黑麦草混播显著降低了降水储存效率和播前含水量，但显著提高了后续冬小麦作物产量和水分利用效率，将填闲作物生物量控制在3.2Mgha-1时可实现粮食产量和水分利用效率最大化。③与冬小麦单作和裸地休闲系统相比，填闲种植能够通过增加根系生物量碳氮输入，增强土壤碳氮固定能力、微生物生物量及其活性，提高系统生产力。④与非豆科填闲作物相比，种植豆科作物或豆科非豆科混播可以通过提高残余质量（碳氮比）减少温室气体排放，同时填闲残余覆盖管理也有利于促进农田减排。⑤与种植黑麦草和怀豆黑麦草混播相比，填闲种植长武怀豆具有更高的地上生物量和更低的温室气体排放强度，在自然降水条件下能够兼顾经济效益与生态效益。⑥填闲种植尤其是豆科填闲作物能够显著促进农田土壤有机碳氮矿化，改善土壤养分，且施氮和增温均能促进填闲作物残余快速腐解，提高碳氮释放速率, 但并不会影响土壤碳氮累积。⑦与裸地休闲相比，填闲种植总体上增强了微生物群落、微生物生物量及其活性，且种植非豆科填闲作物更优于豆科或混播。⑧综合来看，填闲种植虽然降低了农田土壤水分保持能力，但有利于土壤养分供应和作物产量形成，且具有显著的固碳减排效益。相关成果从理论上进一步完善了填闲种植系统知识体系，实践上为填闲种植在黄土高原旱作农业区的恢复与推广提供了科学依据。