冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落的影响

为揭示保护性耕作措施对土壤细菌群落结构及多样性的影响规律，选取免耕覆盖＋施生物有机肥（NF）、免耕覆盖＋不施生物有机肥（NC）、传统耕作不覆盖＋施生物有机肥（TF）和传统耕作不覆盖＋不施生物有机肥（TC）4个处理，以农田土壤生态系统为研究对象，利用16S rDNA基因Illumina MiSeq高通量测序技术，研究了冬小麦免耕覆盖与生物有机肥施用对土壤细菌群落结构及多样性的影响。结果表明：1）与TC处理相比，NF处理显著降低了土壤pH （P=0.03^*），增加了土壤全氮（P=0.002^**）、总碳含量（P=0.0001^**，P=0.007^**），影响了土壤碳/氮比分配（P=0.003^**）。2）从16个土壤样本中共获得细菌27门、86纲、125目、213科和315属，其中放线菌门（Actinobacteria）、酸杆菌门（Acidobacteria）、绿弯菌门（Chloroflexi）和变形菌门（Proteobacteria）为优势菌门，其相对丰度约占总丰度的82.40%。3）与传统耕作施生物有机肥处理相比，免耕覆盖施生物有机肥增加了土壤细菌的多样性指数（Simpson指数和Shannon指数），降低了ACE丰富度指数。4）NMDS及多元分析结果表明：土壤细菌群落丰富度指数、多样性指数均与土壤pH、速效磷和土壤碳/氮比成正相关，与土壤微生物生物量碳（SMBC）和土壤总碳成负相关；其中，土壤pH和SMBC分别是影响酸杆菌门和放线菌门的主要驱动因子。施生物有机肥和耕作措施两种因素均对土壤细菌群落结构组成产生了影响，但以施用生物有机肥对土壤细菌群落多样性的影响较明显；此外，施用生物有机肥在传统耕作和免耕覆盖两种情况下均增加了冬小麦产量，但以传统耕作施生物有机肥处理最明显。因此，传统耕作配施生物有机肥是宁夏南部山区改善土壤理化性质、增加土壤细菌群落丰富度和多样性的重要途径。

Effects of no-tillage mulching and bioorganic fertilizer on soil bacterial community in winter wheat

To examine the impact of conservation tillage on the structure and diversity of soil bacterial communities, we conducted a three year-experiment of winter wheat in mountain areas of southern Ningxia. The experiment included four treatments: no-tillage mulching and bioorganic fertilizer (NF), no-tillage, mulching and no bioorganic fertilizer (NC), conventional tillage without mulching and bioorganic fertilizer (TF), and conventional tillage without mulching and no organic bioorganic fertilizer (TC). By using high-throughput sequencing based on Miseq platform, the V3 and V4 regions of 16S rRNA genes of soil bacteria were analyzed to explore the structure and the diversity of soil bacterial community. The results showed that soil pH of NF treatment significantly decreased (P=0.03^*), total nitrogen (P=0.002^{* *}) and total carbon increased (P=0.0001^{* *}) compared to TC. NF treatment also significantly influenced ratio of total carbon to total nitrogen (P=0.007^{* *}). From 16 soil samples, 13093 bacterial operational taxonomic units (OTUs) from the total of 196423 sequences were obtained. About 27 Phylum, 86 classes, 125 orders, 213 families, and 315 genera of bacteria were identified. Actinobacteria, Acidobacteria, Chloroflexi and Proteobacteria were the dominant phylum of soil bacteria, and the relative abundance of these phylum reached to the 82.40% of the total relative abundance based on the phylum level. Compared to TF, no-tillage mulching and bioorganic fertilizer (NE) increased soil bacterial diversity index (Simpson index and Shannon index), and decreased richness index (ACE index). (NMDS) and multivariate analysis (PCA) showed that the soil bacterial community richness index (ACE and Chao1) and diversity index (Simpson and Shannon) positively related to soil pH, available phosphorus and soil carbon-nitrogen ratio while negatively related to soil microbial biomass carbon (SMBC) and total soil carbon. Soil pH and SMBC were the main driving factors that affected acidobacteria and actinomycetes, respectively. Although both bioorganic fertilizer and tillage were important factors that affected the composition of the soil bacterial community, The effect of bioorganic fertilizer on diversity of the soil bacterial community was greater than tillage did. In addition, bioorganic fertilizer increased the yield of winter wheat under both traditional tillage and no-tillage muclhing, and this yield effect was greater in TF treatment than in the other treatments. The study suggested that conventional tillage with bioorganic fertilizer can be an important way to improve soil physical and chemical properties and increas richness and diversity of soil bacterial community.