Yan Zhengang, Li Wei, Yan Tianhai, Chang Shenghua, Hou Fujiang
State Key Laboratory of Grassland Agro-Ecosystems, Key Laboratory of Grassland Livestock Industry Innovation, Ministry of Agriculture, China, College of Pastoral Agriculture Science and Technology, Lanzhou University, Lanzhou, Gansu Province, China.
College of Information & Science Technology, Gansu Agricultural University, Lanzhou, Gansu Province, China.
PeerJ. 2019 Jun 26;7:e6890. doi: 10.7717/peerj.6890. eCollection 2019.
Agricultural production in Minqin Oasis, China, is commonly categorized as intensive crop production (ICP), integrated crop-livestock production (ICLP), intensive livestock production (confined feeding) (IFLP), and extensive livestock production (grazing) (EGLP). The objectives of the present study were to use a life cycle assessment technique to evaluate on-farm energy balances and greenhouse gas (GHG) emissions of agricultural production, and to compare the differences among the four systems. Data used in the present study were collected from published literature and face-to face questionnaires from 529 farms in eight towns (two towns per production system) within Minqin county. The ANOVA of averaged data from 2014 to 2015 indicated that the net energy ratio (Output/Input) for the EGLP system was significantly higher than that for any other system ( < 0.01), whereas the difference among other three systems were not significant. The EGLP system generated lower CO-eq emissions per hectare of farmland than other systems ( < 0.01). Relating carbon economic efficiency to market values (US$) of agricultural products, indicated that the carbon economic efficiency (US$/kg CO-eq) of the IFLP system was significantly greater than that of other systems ( < 0.01). The major GHG emission sources varied across the systems, that is, soil respiration is the dominant source in EGLP, while the main sources in IFLP are enteric methane and manure management; in ICLP major sources are enteric methane, soil respiration and fertilizer; and in ICP are soil respiration and fertilizer. The structural equation modelling analysis showed that livestock category was strongly linked to net income. The direct effects and total effects of water use efficiency, via its positive influence on energy balances and GHG emissions were much stronger than those of other dependent variables. The study provides important benchmark information to help develop sustainable agricultural production systems on energy balances and GHG emissions in northwestern China.
中国民勤绿洲的农业生产通常分为集约作物生产（ICP）、作物-畜牧综合生产（ICLP）、集约畜牧生产（圈养）（IFLP）和粗放畜牧生产（放牧）（EGLP）。本研究的目的是运用生命周期评估技术，评估农业生产的农场能源平衡和温室气体（GHG）排放，并比较这四种系统之间的差异。本研究使用的数据来自已发表的文献以及对民勤县八个镇（每个生产系统两个镇）529个农场的面对面问卷调查。对2014年至2015年的平均数据进行方差分析表明，EGLP系统的净能量比（产出/投入）显著高于其他任何系统（<0.01），而其他三个系统之间的差异不显著。EGLP系统每公顷农田产生的CO₂当量排放量低于其他系统（<0.01）。将碳经济效率与农产品市场价值（美元）相关联，表明IFLP系统的碳经济效率（美元/千克CO₂当量）显著高于其他系统（<0.01）。不同系统的主要温室气体排放源各不相同，即土壤呼吸是EGLP的主要排放源，而IFLP的主要排放源是肠道甲烷和粪便管理；ICLP的主要排放源是肠道甲烷、土壤呼吸和肥料；ICP的主要排放源是土壤呼吸和肥料。结构方程模型分析表明，畜牧类别与净收入密切相关。水分利用效率通过对能量平衡和温室气体排放的积极影响，其直接效应和总效应比其他因变量要强得多。该研究提供了重要的基准信息，有助于在中国西北开发关于能源平衡和温室气体排放的可持续农业生产系统。
