关键词: 稻油轮作, 秸秆还田, 生物炭, 产量稳定性, 周年能值产量, 氮素吸收量, 氮收获指数

Abstract:

【Objective】Rice-rapeseed rotation is a major cropping system in the Yangtze River basin of China. Straw utilization is a crucial issue concerning agricultural sustainable development and environmental protection. This study aimed to explore the fertilizer-based utilization methods of straw in rice-rapeseed rotation systems, so as to provide the theoretical support for enhancing productivity and achieving efficient resource utilization in such systems.【Method】This study utilized a six-year (2017-2023) field experiment under rice-rapeseed rotation. Four treatments were chosen: no straw incorporation (NPK), direct incorporation of straw in both seasons (NPK+S/S), straw biochar incorporation in both seasons (NPK+B/B), and straw biochar incorporation in the rice season combined with direct straw incorporation in the rapeseed season (NPK+B/S). Crop yield and its stability, plant N absorption and utilization efficiency as well as the apparent N balance in soil were systematically analyzed.【Result】Direct and straw biochar incorporation significantly increased crop yields and yield stability. Compared with NPK, the rapeseed yields under NPK+S/S, NPK+B/B, and NPK+B/S increased by 13.9%, 14.8%, and 17.3% on average, respectively; rice yields increased by 8.5%, 7.2%, and 3.7%, respectively; annual energy yields improved by 10.5%, 9.9%, and 8.5%, respectively. Compared with NPK, the rapeseed yield sustainability index under NPK+S/S, NPK+B/B, and NPK+B/S was enhanced by 8.1% to 10.2%. Compared with NPK+S/S, NPK+B/B and NPK+B/S were more beneficial for enhancing rice yield stability (24.2% and 1.4%, respectively) and sustainability index (5.3% and 2.3%, respectively). Both straw management practices increased crop N uptake but decreased the N harvest index. Compared with NPK, aboveground N uptake in rapeseed increased by 7.4% to 20.7%, in rice by 3.3% to 15.0%, and in the annual rotation by 6.5% to 17.6% under NPK+S/S, NPK+B/B, and NPK+B/S treatments. However, the N harvest index in rapeseed and rice decreased by 0.2%-3.0% and 1.9%-3.8%, respectively. Compared with NPK+S/S treatment, NPK+B/B treatment significantly reduced N uptake in the above-ground part of rapeseed by 11.0%. The reduction in N uptake in rapeseed grains, rice grains, and the above-ground part of rice was not significant, while the N harvest index of rapeseed and rice was increased by 1.8% and 1.9%, respectively. Direct straw incorporation had an advantage in promoting crop N uptake, while straw biochar incorporation had an advantage in improving crop N distribution. Compared with NPK, NPK+S/S, NPK+B/B, and NPK+B/S significantly increased the partial factor productivity of applied N in rapeseed (13.9% to 17.2%) and rice (2.2% to 7.7%). All treatments showed N surplus, with the NPK+B/S treatment having the highest N surplus. Compared with the NPK treatment, the NPK+S/S, NPK+B/B and NPK+B/S treatments all increased the soil total N content (20.6%-22.7%). Soil total N content was the highest under straw biochar incorporation, which was more effective in converting surplus N into soil N and reducing N loss.【Conclusion】In rice-rapeseed rotation system, considering economic effects, compared with direct straw incorporation or straw biochar incorporation in both seasons, the strategy of applying straw biochar during the rice season and directly incorporating straw during the rapeseed season could not only ensure stable high crop yields but also enhance N fertilizer utilization and increase soil total N content, providing important support for the sustainable development of rice-rapeseed rotation systems.

Key words: rice-rapeseed rotation, straw incorporation, biochar, yield stability, annual energy yield, nitrogen absorption, nitrogen harvest index