生物炭对植烟土壤氮循环微生物及其功能基因的影响

Effects of biochar on nitrogen cycling microbes and their functional genes in tobacco-growing soils

  • 摘要: 【目的】探讨土壤氮循环微生物及其功能基因对生物炭改良的响应,阐明土壤理化因子与氮循环微生物之间的互馈机制,为生物炭改良土壤、提高作物氮素利用率及调控土壤氮循环过程提供理论依据。【方法】以烤烟品种云烟87为试验材料,通过全层生物炭改良(T1,30 t/ha)与不施生物炭(T0,对照)的对比,采用宏基因组学与qRT-PCR相结合的方法分析生物炭对烟株氮素积累量及烤烟根际土壤理化性质、氮循环相关微生物相对丰度和功能基因表达量的影响。【结果】与对照T0处理相比,2021和2022年T1处理烤烟氮素积累量显著提高45.75%和29.91%(P<0.05,下同)。土壤碱解氮与硝态氮含量也较T0处理显著提高,而铵态氮含量则显著降低。宏基因组学分析结果表明,在微生物门水平上,T1处理较T0处理显著提高了根际土壤中奇古菌门(Thaumarchaeota)、酸杆菌门(Acidobacteriota)、绿弯菌门(Chloroflexi)及硝化螺旋菌门(Nitrospirae)相对丰度,其中奇古菌门相对丰度较T0处理提高23.76%;属水平上,与T0处理相比,T1处理亚硝化杆菌属(Candidatus_Nitrosotalea)相对丰度提高20.83%;在氮循环功能亚类上,T1处理较T0处理显著提高土壤氮循环过程中硝化作用nxrA、氨氧化作用amoA及固氮作用nifA的基因相对表达量,分别提高20.08%、250.37%和82.45%,同时反硝化作用的norB基因相对表达量降低39.76%。qRT-PCR验证分析表明施用生物炭对土壤氮循环过程的调控具有一定的持续性。冗余分析结果发现,土壤pH、无机氮含量与容重、孔隙度等理化性质是影响土壤氮循环的重要环境因子。相关分析结果表明,土壤pH、硝态氮含量及容重等理化性质与硝化、氨氧化微生物丰度及基因表达量均呈极显著正相关(P<0.01)。【结论】在烟—稻轮作区采用30 t/ha生物炭进行植烟土壤改良有利于改善土壤理化特性,进而驱动土壤氮循环向氮高效利用途径转化,从而促进烟株氮素吸收。

     

    Abstract: 【Objective】The purpose of this study was to explore the response of soil nitrogen cycling microbes and the functional genes to biochar,and to clarify the mutual feedback mechanism between soil physicochemical properties and nitrogen cycling microbes,so as to provide theoretical basis for improving soil,improving crop nitrogen use efficiency and regulating soil nitrogen cycle process.【Method】The effects of biochar on nitrogen accumulation in plants, the physicochemical properties of tobacco rhizosphere soil,the relative abundance of nitrogen cycling microor-ganisms,the expression of their functional gene were analyzed by a combination of metagenomics and qRT-PCR using the variety Yunyan 87as the test material,comparing the biochar improvement by soil tillage layer(T1,30 t/ha)and no biochar application(T0,control).【Result】Compared to control T0,nitrogen accumulation in flue-cured tobacco was significantly increased by45.75% and 29.91% at T1 treatment in 2021 and 2022,respectively(P<0.05,the same below). At the same time, soil alkali-hydrolyzed nitrogen and nitrate nitrogen content in T1 treatment were significantly increased, while ammonium nitrogen content was significantly decreased compared to control T0 treatment. Metagenomics analysis showed that T1 treatment significantly increased the relative abundances of Thaumarchaeota,Acidobacteriota,Chloroflexi and Nitrospirae at the phylum level in rhizosphere soil compared to T0 treatment,among which the relative abundance of Thaumarchaeota increased by 23.76%. At the genus level,the relative abundance of Candidatus_Nitrosotalea in T1 treatment was significantly increased by 20.83% compared to T0 treatment. In terms of nitrogen cycle function subcategories,T1 treatment significantly increased the relative expression of nitrification nxrA,ammonia oxidation amoA and nitrogen fixation nifA genes in the process of soil nitrogen cycle by 20.08%,250.37% and 82.45% respectively,compared to T0 treatment. While reducing the relative expression of denitrification norB genes by 39.76%. qRT-PCR analysis results showed that the addition of biochar had a certain persistence in the change of soil nitrogen cycle process. The further redundancy analysis found that soil pH,inorganic nitrogen content,bulk density,porosity and other physical properties were important environmental factors affecting soil nitrogen cycle. Pearson correlation analysis found that soil pH,nitrate nitrogen and physical properties were significantly positively correlated with nitrification and ammonia oxidizing microbes abundance and genes expression(P<0.01).【Conclusion】The improvement of tobacco planting soil with 30 t/ha biochar is beneficial to improve soil physicochemical properties and then drive the transformation of soil nitrogen cycle to efficient nitrogen utilization pathway,thereby promoting nitrogen absorption by plants in tobacco-rice cropping area.

     

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