Emergy analysis, water-heat utilization, and carbon emission of typical cropping patterns in the oasis irrigation area.

Abstract

Reasonable cropping pattern can improve resource utilization efficiency, reduce environmental risks in agricultural production, and achieve the goal of resource saving coupled with high production and efficiency. We evaluated the production effects of typical cropping patterns in an arid irrigation region from several aspects, including resource utilization, carbon emissions, economic benefit, emergy self-sufficiency ratio and net emergy yield ratio, with the method of emergy theory, to provide theoretical and practical basis for the establishment of efficient cropping with lower resource investment and carbon emissions but higher yield and resource utilization efficiency combined with the sustainability of agricultural production. The results showed that, high-efficient wheat-maize intercropping production pattern (integration of no tillage with 25 to 30 cm height of wheat straw covering in the wheat strip and two-year plastic mulching in the maize strip, NTSI) had the best performance in grain yield boosting, with the yields 13.5% to 16.9% and 13.8% to 17.1% higher than that in local traditional production patterns (i.e., wheat-maize intercropping, CTI, and monoculture maize, CTM), respectively. Moreover, NTSI increased water use efficiency and solar energy use efficiency by 12.4% to 17.2% and 6.1% to 8.1%, compared to CTI, respectively. Compared to CTI and CTM, NTSI improved the effect on carbon emission reduction by decreasing total soil CO2 emission by 618 to 895 kg·hm-2 and 1804 to 2002 kg·hm-2 with the ratio of 12.1% to 16.4% and 28.6% to 31.0%, but increased carbon emission efficiency by 29.3% to 40.1% and 58.9 to 71.4%, respectively. Meanwhile, the NTSI pattern had obvious resources saving potential. Compared with CTI and CTM, NTSI reduced total input by 1424 to 1431 yuan·hm-2 and 501 to 1547 yuan·hm-2, with the proportional reduction being 12.6% to 13.6% and 4.9% to 14.6%; however, increased total output by 4309 to 4603 yuan·hm-2 and 8439 to 11057 yuan·hm-2, the increased ratio was 11.2% to 11.8% and 24.4% to 36.3%; also, increased net return by 5740 to 6027 yuan·hm-2 and 9544 to 11558 yuan·hm-2, and the improved percentage was 19.6% to 22.4% and 40.1% to 57.7%, respectively. Therefore, the high-efficient NTSI pattern had greater input-output ratio by 27.9% to 29.0% and 40.5% to 45.6% than CTI and CTM, respectively, similarly, greater benefit per cubic meter of water by 19.9% to 23.2% and 27.7% to 39.3%, respectively. The emergy self-sufficiency ratio of NTSI pattern was 57.2%, being 4.0% and 12.2% higher than CTI and CTM, respectively. NTSI pattern's net emergy yield ratio was 0.173, being 10.0% greater than CTI but 11.7% lower than CTM. With respect to resource utilization, carbon emission reduction, economic benefits and the sustainable development of high-efficient intercropping pattern, the integration of no tillage with straw covering and two-year plastic film mulching measures had higher economic activity, better function of agricultural system, greater production efficiency, and higher returns on energy value. We concluded that NTSI could be a high-efficiency farming system pattern on resources saving, carbon emission reduction, high yield and efficiency in arid oasis irrigation areas.