Evaluation of energy balances and greenhouse gas emissions from different agricultural production systems in Minqin Oasis, China

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 (LCA) to evaluate the on farm energy balances and greenhouse gas (GHG) emissions of agricultural production, and to compare the differences among the four systems. 529 farmers in eight towns of Minqin Oasis were selected to complete a face-to-face questionnaire. AVONA analysis of the average data from 2014 to 2015 indicated that the net energy ratio (Output/Input) for the EGLP system was significantly higher than for each of the other three systems (P < 0.01), whereas the differences among the other systems were not significant. However, the EGLP system generated lower CO₂-eq emissions per hectare of farmland than each of the three other systems (P < 0.01). Relating carbon economic efficiency to market values (Chinese currency, ¥) of agricultural products, indicated that the carbon economic efficiency (¥/kg CO₂-eq/farm) of the IFLP system was significantly greater than that of the three other systems (P < 0.01). The net energy ratios of alfalfa (4.01) and maize (2.63) were significantly higher than the corresponding data of the other crops (P < 0.01). All of the emission sources data for ICP, ICLP, IFLP, and EGLP, when related to the contribution of GHG emissions, showed fertilizer, enteric methane emissions, and plastic mulch, contributed the highest proportions of GHG emissions of all production categories. The path models showed that class of livestock was strongly linked to economic income. The direct effects and total effects of water use efficiency, via their positive influence on energy balances and GHG emissions were much stronger than those of other dependent variables. In conclusion, the present study provides benchmark information on the factors for energy balances and GHG emissions for agricultural production systems in northwestern China.