Abstract: This study aims to delineate the disparities in greenhouse gas (GHG) emissions from the cultivation of food and forage crops,and to pinpoint significant emission sources. Drawing on 738 valid household questionnaire surveys executed in Gansu and Ningxia from 2018 to 2021,the GHG emissions from four principal crops (wheat,maize,alfalfa,and forage maize) were assessed using the Life Cycle Assessment method. The research revealed that the per-hectare dry matter yields of wheat,maize,alfalfa,and forage maize were 6.45,16.81,6.28,and 17.05 tons,respectively;while the per-hectare crude protein yields were 0.52,1.08,0.79,and 1.22 tons,respectively. Besides,the GHG emissions per hectare of wheat,maize,alfalfa,and forage maize were 3.89,5.14,1.12,and 4.34 tons of CO₂ equivalent,respectively. With dry matter and crude protein as functional units,forage crops,especially alfalfa,demonstrated lower emissions. Sensitivity analysis revealed that fertilizers and agricultural machinery were the primary contributors to GHG emissions,collectively representing an average of 75.29% and 11.51%,respectively. Hence,we propose substituting food crops with forage crops to facilitate herbivorous animal husbandry in the study area. Implementing improved crop fertilization management and increasing mechanical efficiency can significantly contribute to GHG mitigation in herbivorous animal husbandry.

Key words: Forage crop, Greenhouse gases, Life cycle assessment, Cereal shift to forage production

摘要： 为探究粮食作物和饲草作物生产在温室气体排放方面的差异，识别潜在的减排热点，本研究基于2018—2021年在甘肃和宁夏获得的738份有效农户问卷调查数据，以小麦、玉米、苜蓿和饲用玉米四种作物为研究对象，使用生命周期评价的方法评估温室气体(CO₂当量)排放量。结果表明，研究区域每公顷的小麦、玉米、苜蓿、饲用玉米干物质产出分别为：6.45，16.81，6.28，17.05 t；蛋白质产出分别为：0.52，1.08，0.79，1.22 t。四种作物的温室气体排放量分别为：3.89，5.14，1.12，4.34 t·hm^-2；但在每吨干物质和蛋白质产出基准下，苜蓿与饲用玉米均显示较低的排放强度，其中苜蓿的优势更为显著。敏感度分析表明，化肥和农机使用对排放结果的敏感度平均达到75.29%和11.51%。因此，建议研究区域使用优质饲草作物替代粮食作物支撑草食畜牧业，同时加强作物的田间施肥管理和提高机械使用效率，能有效地减少草食畜牧业在饲料生产端的温室气体排放量。

关键词: 饲料作物, 温室气体, 生命周期评价, 粮改饲