秸秆还田方式对根际固氮菌群落及花生产量的影响

Effects of different types of straw returning on nitrogen-fixing bacteria community in rhizosphere and peanut yield

【目的】固氮微生物是土壤中重要的功能微生物,其多样性和群落组成变化能够影响土壤氮素固定与氮循环过程,探究不同秸秆还田方式对根际土壤固氮菌多样性和群落组成的影响机制具有重要意义。【方法】基于中国科学院鹰潭红壤生态实验站花生单作系统不同秸秆还田长期定位试验,设置不施肥对照(CK)、单施化肥(NPK)、NPK肥+秸秆还田(NPKS)、NPK肥+秸秆猪粪配施(NPKSM)和NPK肥+秸秆生物炭(NPKB) 5个处理,利用高通量测序技术,分析不同秸秆还田方式下根际固氮菌多样性和群落组成的变化特征。【结果】秸秆还田处理下土壤有机碳(SOC)、速效钾、全磷、有效磷、全氮含量提升,其中以NPK肥+秸秆猪粪配施(NPKSM)处理效果最佳。秸秆还田增加了固氮微生物多样性,并显著改变其群落组成,在纲水平上固氮菌以α-变形菌纲(Alphaproteobacteria,82.5%)为优势类群;在属水平上以慢生根瘤菌属(Bradyrhizobium,51.9%)为优势类群。土壤有效磷是影响固氮菌多样性指数的主要因素,而土壤pH、SOC、速效钾、全磷、有效磷、全氮和铵态氮是影响固氮菌群落组成的主要因素。结构等式方程研究结果表明土壤有效磷和全氮通过改变δ-变形菌纲(Deltaproteobacteria)的相对丰度和固氮菌群落组成间接影响花生产量。【结论】秸秆还田显著提升了土壤肥力,土壤有效磷是根际固氮菌多样性和群落组成改变、花生产量提高的重要驱动因素,通过提高Deltaproteobacteria的相对丰度促进了花生增产。本研究为建立合理的秸秆还田措施,增强生物固氮潜力以及提升红壤肥力与健康提供科学依据。

【Objectives】Nitrogen-fixing bacteria are an important functional group in the soil microbial community.The changes in the diversity and structure of nitrogen-fixing bacterial community can affect soil nitrogen fixation and nitrogen cycle dynamics.Here,we explored the mechanism of the diversity and structure of rhizosphere nitrogen-fixing bacterial community in regulating peanut yield under the different straw returning treatments.【Methods】We conducted the long-term field experiment with different types of straw returning in peanut mono-cropping system at the Yingtan National Agroecosystem Field Experiment Station of the Chinese Academy of Sciences in Jiangxi.The field experiment included five treatments:no fertilization(CK),conventional NPK(NPK),NPK with straw(NPKS),NPK with straw and pig manure(NPKSM),and NPK with straw biochar(NPKB).The illumina sequencing of nifH gene was used to investigate the diversity and structure of nitrogen-fixing bacterial community in the rhizosphere.【Results】The treatments with straw returning significantly promoted soil fertility including soil organic carbon(SOC),available K,total P,available P,total N,with the highest values under the NPKSM treatment.Compared with the CK and NPK treatments,the NPKS and NPKSM treatments significantly increased the diversity of soil nitrogen-fixing bacteria and shaped community composition.Alphaproteobacteria(82.5%)was the dominant class in the nitrogen-fixing bacteria community,and Bradyrhizobium(51.9%)was the dominant genus.Soil available P was the most important predictor of the nitrogen-fixing bacterial diversity,while pH,SOC,available K,total P,available P,total N and ammonia nitrogen(NH_(4)^(+)-N)were the significant predictors of the nitrogen-fixing bacterial community composition.Structural equation modeling suggested that available P and total N was indirectly associated with peanut yield by changing the structure of nitrogen-fixing bacterial community.【Conclusions】Straw returning significantly improved soil fertility,and available P was an important factor in driving the nitrogen-fixing bacterial community composition and peanut yield by enhancing the relative abundance of Deltaproteobacteria.Taken together,our study provides the scientific basis for establishing reasonable measures of straw returning to promote the potential of biological nitrogen fixation,and to improve the fertility and health of red soil.