化肥有机替代对连作花生田土壤有机碳和微生物群落的影响

Effects of organic substitution of chemical fertilizers on soil organic carbon and microbial community in continuous cropping peanut fields

为揭示化肥有机替代措施下连作花生田土壤有机碳(SOC)积累的微生物机制,在连作5年的花生田设置了蚯蚓粪配施化肥(VM)、生物有机肥配施化肥(BF)、全量化肥(CF)和无施入对照(CK)4个处理,采用磷脂脂肪酸法(PLFA)分析了土壤微生物群落组成及多样性,测定了SOC及其组分含量以及花生产量,分析了化肥有机替代、SOC和土壤微生物群落三者间的关系。结果表明:花生连作土壤环境严重恶化并显著影响了花生产量,而有机肥部分替代化肥明显提高了SOC和各组分含量以及土壤微生物生物量,改变了土壤微生物群落组成及其多样性,提高了花生产量,其中VM处理效果最显著(P<0.05)。与CK相比,VM处理的花生产量增加了56%,SOC含量增加了11.4%,土壤总PLFA含量增加了149.4%。冗余分析和逐步回归分析表明,VM和BF处理与SOC及其各组分含量、土壤微生物各类群PLFA含量均呈正相关,尤其VM处理相关性最强(P<0.05);CK和CF处理与除了G+/G-比值以外的其他所有变量均呈负相关;SOC各组分含量与土壤微生物各类群PLFA含量显著相关。综上,化肥有机替代导致的外源有机碳增加以及随后引起的土壤微生物群落的变化是连作花生田SOC积累的驱动因素,土壤微生物活性是影响SOC累积的关键因素。有机肥特别是蚯蚓粪部分替代化肥是改善连作花生田土壤质量、缓解连作障碍的有效措施。

To reveal the microbial mechanisms of soil organic carbon(SOC) accumulation in continuous peanut cropping fields under organic substitution of chemical fertilizers, we carried out a five-year experiment with the treatments of vermicompost combined with chemical fertilizer(VM), bio-organic fertilizer combined with chemical fertilizer(BF), total-chemical fertilizer(CF) and no-fertilizer control(CK) in a continuous peanut cropping field. The composition and diversity of soil microbial community were tested by the phospholipid fatty acid method(PLFA). The contents of SOC and its components, peanut yields as well as the relationships between organic substitution, SOC and soil microbial community were analyzed. The results showed that the continuous peanut cropping seriously deteriorated soil environment and peanut yield, whereas the partial replacement of chemical fertilizers with organic fertilizers significantly increased the contents of SOC and its components and soil microbial biomass, changed the composition and diversity of soil microbial community, and enhanced peanut yield, with the most significant effect in the VM treatment(P<0.05). Compared with CK, the peanut yield of VM treatment increased by 56%, the SOC content and the total PLFA content increased by 11.4% and 149.4%, respectively. The results of redundancy analysis and stepwise regression analysis showed that VM and BF treatments were positively associated with the contents of SOC and its components and the PLFA contents of various soil microbial groups, especially in the VM treatment(P<0.05). The CK and CF treatments were negatively associated with all response variables except G+/G-ratio. The contents of SOC components were significantly correlated with the PLFA contents of various soil microbial groups. In conclusion, the organic substitution of chemical fertilizers induced increase of exogenous organic carbon and subsequent changes in soil microbial community which were the driving factors for SOC accumulation, and soil microbial activity was the key factor affecting SOC accumulation. Partial replacement of chemical fertilizers by organic fertilizers, especially vermicompost, is an effective strategy to improve soil quality in continuous peanut cropping fields and alleviate the obstacles in continuous cropping.