连续秸秆–紫云英协同还田对双季稻产量、养分积累及土壤肥力的影响

  【目的】  水稻秸秆和紫云英是稻田系统重要的原位有机肥源，明确长期连续秸秆–紫云英协同还田后水稻增产趋势、养分积累和土壤肥力变化特征，以便对秸秆和绿肥资源进行综合利用。  【方法】  本试验为3年连续大田试验 (2016―2018年)，以双季稻为研究对象，设置3个处理:1）早、晚稻秸秆不还田，冬季不种植紫云英 (CK)；2）早、晚稻秸秆全量还田，冬季不种植紫云英，即秸秆单独还田 (T1)；3）早、晚稻秸秆全量还田，冬季种植紫云英，即秸秆–紫云英协同还田 (T2)。各处理均施用等量化肥。  【结果】  相对于对照，连续秸秆单独还田和秸秆–紫云英协同还田周年轮作下水稻产量分别增加1.93%～9.15%和1.34%～12.48%，且连续秸秆–紫云英协同还田周年增产效果随着试验年份的增加而增加。不同年份间水稻产量变异系数和可持续性指数分析表明，连续秸秆单独还田和秸秆–紫云英协同还田均有利于双季稻持续性高产稳产，其中秸秆–紫云英协同还田效果优于秸秆单独还田。连续3年6季还田后，秸秆单独还田和秸秆–紫云英协同还田对水稻产量的贡献率分别为6.92%和11.10%，其中秸秆–紫云英协同还田处理比秸秆单独还田处理高76.47%。与产量变化趋势一致，连续秸秆–紫云英协同还田不仅有利于早稻氮、磷、钾养分积累，对晚稻养分积累也有一定的后效作用。与试验初始土壤养分含量相比，2018年晚稻收获后，对照土壤有机碳、全氮、有效磷和速效钾含量分别降低了9.03%、11.11%、3.87%和10.57%。而相对于对照，连续秸秆–紫云英协同还田处理土壤有机碳、全氮、有效磷和速效钾含量分别增加了20.51%、25.00%、24.16%和20.37%；相对于秸秆单独还田处理有机碳、全氮和有效磷含量分别增加了2.73%、7.14%和14.19%。  【结论】  在双季稻轮作系统中，连续秸秆–紫云英协同还田有利于早稻和晚稻获得高产和稳产，同时增加早稻氮、磷、钾养分积累，提高土壤有机碳、全氮和有效磷含量，是综合利用秸秆和绿肥资源较好的方式。

Effect of continuous straw-Chinese milk vetch synergistic return to the fieldon yield,nutrient accumulation and soil fertility of double cropping rice

  【Objectives】  Rice straw and Chinese milk vetch are important in-situ organic fertilizer resources in the paddy cultivated system. The trend of rice yield increase, nutrient accumulation and soil fertility change characteristics after continuous straw-Chinese milk vetch synergistic return to the field were analyzed to make comprehensive utilization of straws and green fertilizer resources.  【Methods】  The field experiment was conducted from 2016 to 2018 under double-cropping rice system, covering 6 seasons. Three treatments included: neither rice straw returning nor Chinese milk vetch planting in winter (CK); whole rice straws returning but no Chinese milk vetch planting (T1); whole rice straws returning and Chinese milk vetch planting (T2). The chemical fertilizer was applied in the same way and rate for all the three treatments. The rice yield, nutrient absorption and soil fertility were analyzed.  【Results】  Compared with the CK, the annual rice yields in T1 and T2 were increased over the experimental years, and in range of 1.93%–9.15% and 1.34%–12.48%, respectively. According to the analysis on rice yield variation coefficient and sustainability index, both the T1 and T2 treatments were in favor of keeping sustainable and high annual yields of rice, and T2 performed better than T1 did. The contribution rates of straw returning in T1 and T2 were 6.92% and 11.10%, respectively, with that of T2 higher than T1. The T2 treatment significantly increased the accumulation of N, P and K in early rice, and also in late rice due to the aftereffect. After the late rice harvest in 2018, the soil organic matter, total N, available P and K contents were reduced by 9.03%, 11.11%, 3.87% and 10.57% in T1 compared with those in the begin of experiment, while they were increased by 20.51%, 25.00%, 24.16% and 20.37% in T2 compared with CK, and organic carbon, total nitrogen and availabl phosphorus contents in T2 were increased by 2.73%, 7.14% and 14.19% compared to those in T1.  【Conclusions】  In the double-season rice rotation system, the co-returning of rice straw and Chinese milk vetch is more effective than sole straw returning in stimulating the NPK accumulation in rice, maintaining the high and stable yields of both early and late rice, and at the same time improving soil fertility.