Comparison of ecological evaluation results on conservation tillage by different methods

Abstract: Comprehensive evaluation on agricultural production technologies can provide scientific base for technology application for agriculture production. However, a good comprehensive evaluation on agricultural production system must integrate the economic, ecological and environmental aspects of a production system. Agricultural production should not only focus on the yield increasing, but also should avoid the degradation of ecosystem services and alleviate the negative environmental impacts. Therefore, when selecting an appropriate agricultural technology for a production system, a comprehensive evaluation is needed for decision-make process. In recent decades, many kinds of theories and methods in the ecological economic research have been developed and some are used widely, such as emergy, ecosystem services, ecosystem health, ecological footprint, life cycle assessment, etc. However, each method has its independent theory base and calculation process. In additional, single method is hard to meet the multi-aspect evaluation needs. Therefore, to compare the results of different ecological evaluation methods, three methods including emergy (EM), ecosystem services (ES) and life circle assessment (LCA) were used in this research to evaluate economic, ecological and environmental concerns of an agricultural production technology. Four kinds of conservation tillage (CT) patterns in Jilin province, northeastern of China were taken as case study. The four CT patterns include 'direct-seeding on ridge side and standing-stubble return' (CT1), 'wide/narrow row alternation planting and high stubble mulching' (CT2), 'stubble mulching and direct-seeding on ridge' (CT3) and 'cutting stubble combined ridge with subsoiling' (CT4). The results showed that four kinds of CT methods had a consistent trend of advantage of eco-ecological effects compared to the conventional tillage (CK). Based on evaluation result of EM, the average value of EYR (emergy yield ratio) of the four CT methods was 9.6% higher than that of CK. The ESI (emergy sustainability index) of the four CT methods was 7.0% higher than that of CK. The total average value of ES of the four CT methods was about 2.1 times higher than that of CK. For the results of LCA, as compared to CK, the potential environmental effect of the four CT methods in term of energy consumption, greenhouse gas emission, acidification and eutrophication were lower, which accounted for 14.62%, 82.82%, 15.37% and 15.28% respectively of the CK (100%). The results also showed that the ranking order for the four CT were different for each of the evaluating result of EM, ES and LCA. For the result of emergy, the ranking of the four conservation tillage was: CT3>CT4>CT2>CT1. However, the ranking order was CT2>CT1>CT3>CT4 for ES and CT2>CT3>CT4>CT1 for the LCA method. These results indicated that multiple methods were needed for holistic evaluating the eco-ecological effects of agricultural technology. From our results we found that the EM method was mainly suited for evaluating the energy use efficiency and economic benefit, the ES method was more on the ecologic functions of maintenances, the LCA was suited for assessing the environmental impacts. The three methods were recommended as an integrated evaluation for agricultural technologies. Finally, combining evaluation results from of EM, ES and LCA, the ranking of the four CT methods was CT2>CT3>CT4>CT1. This research provided a comprehensive scientific tool for decision-making processes for agriculture technology selection, adoption and extension.