冬小麦免耕覆盖与有机栽培对土壤微生物群落组成的影响

Effects of no-tillage, mulching and organic fertilization on soil microbial composition in winter wheat field

为揭示农业管理活动对土壤微生物群落结构及AM真菌多样性的影响,以农田土壤生态系统为研究对象,选取免耕覆盖+施有机肥(NF)、免耕覆盖+不施有机肥(NC)、传统耕作不覆盖+施有机肥(TF)和传统耕作不覆盖+不施有机肥(TC)4种处理,采用IlluminaMiseq高通量测序及磷脂脂肪酸(phospholipidfattyacids,PLFAs)分析方法,研究持续冬小麦免耕覆盖有机栽培3年后,土壤微生物群落结构组成、AM真菌及其多样性与土壤环境因子间的关系。结果表明,持续免耕覆盖有机栽培能增加以PLFA表征的土壤微生物群落的生物量,传统耕作显著提高了土壤革兰氏阳性菌(G+)、阴性菌(G?)的生物量(P<0.05)。且随免耕栽培管理年限增加,土壤AM真菌生物量呈显著上升趋势;以16:1ω5c中性脂(NLFA)与16:1ω5c磷脂(PLFA)表征的AM真菌生物量比值显著升高(P<0.05)。免耕覆盖措施下,有机肥的施用提高了土壤AM真菌丰富度指数(Chao1指数和ACE指数),但降低了土壤AM真菌的多样性(香农指数、辛普森指数)。主成分分析结果显示, AM真菌孢子(16:1ω5c中性脂)的生物量与土壤有机质、土壤易提取球囊霉素含量呈正相关关系, AM真菌丰富度指数与土壤有机质含量呈正相关, AM真菌多样性指数与土壤全氮含量、脲酶活性呈正相关。受农业管理措施导致的土壤理化性状及土壤生物学差异等综合因素影响,土壤微生物生物量及AM真菌多样性和丰富度改变。免耕覆盖措施提高了土壤AM真菌多样性指数,有机肥施用显著影响了AM真菌NLFA/PLFA生物量的比例,改变了AM真菌孢子和菌丝间生物量碳的分配关系。

Soil micro-organisms constitute a significant part of soil fertility and play a critical role in maintaining soil ecological functions.Micro-organisms also are key indicators for soil quality and productivity.No-tillage and mulching cultivation indirectly affect the composition of soil microbial community by changing plant physiological characteristics and root exudates.The two agronomic practices can also improve soil environment by increasing the total amount of micro-organisms in the soil.By analyzing the composition of soil microbial community under no-tillage,mulching and organic cultivation of winter wheat in the southern mountain areas of Ningxia,the effects of agricultural management activities on soil microbial community structure and arbuscular mycorrhizal(AM)fungal diversity were determined in this paper.The study aimed at providing theoretical basis for the promotion of long-term no-tillage,mulching cultivation,sustainable use of farmlands and maintenance of soil microbial diversity.Short-term test on conservation tillage(no-tillage)was done for three consecutive years in Longde County,Guyuan.Four soil treatments were selected including no-tillage and straw mulching without organic fertilizer application(NC),no-tillage and straw mulching with organic fertilizer application(NF),traditional tillage and no-mulching without organic fertilizer application(TC)and traditional tillage and no-mulching with organic fertilizer application(TF).By using Illumina Miseq high-throughput sequencing platform and phospholipid fatty acids(PLFAs)analysis methods,soil microbial community composition,AM fungi community composition and diversity and soil environmental factors were analyzed after three years cultivation of winter wheat.The results showed that continuous no-tillage,mulching and organic fertilizer application increased soil microbial community biomass characterized by PLFA.Traditional tillages significantly improved microbial community biomass(P<0.05)of gram-positive(G^+)and negative(G^-)bacteria in the soil.With increasing years of management of no-tillage and straw mulching,soil AM fungi biomass significantly increased.Also biomass ratios of 16:1ω5c neutral lipid(NLFA)to 16:1ω5c phospholipid lipid(PLFA)significantly increased(P<0.05).Under no-tillage and straw mulching,the application of organic fertilizer increased soil AM fungi richness index(Chao1 index and ACE index),but reduced soil AM fungi diversity(Shannon index and Simpson index).The results of principal component analysis showed that biomass of AM fungal spores(16:1ω5 c neutral fat)was positively correlated with soil contents of organic matter,and easily extracted glomalin.While AM fungi richness index was positively correlated with soil organic matter content,AM fungi diversity index was positively correlated with soil total nitrogen content and urease activity.AM fungi richness and diversity were affected by soil physical and chemical properties and soil biological differences.Also soil microbial biomass changed along with AM fungal diversity and richness.It was concluded that no-tillage and straw mulching cultivation increased soil AM fungi diversity.The proportion of NLFA to PLFA biomass of AM fungi was also significantly affected by the application of organic fertilizer,and changed distribution of biomass carbon between AM fungi spores and mycelium.