Difference Of N₂o Consumption Potential In Typical Rice Soils And The Relationship With The Abundance Of Nitrous Oxide Reductive Microorganisms

Nitrous oxide is one of the three major greenhouse gases and has a destructive effect on the atmosphere.Farmland soil is considered as the most important source of N₂O emissions.In recent years,researchers have found that N₂O emissions in soil is accompanied by negative emissions meanwhile,and it is believed that this phenomenon is a microbial-mediated biological pathway that can truly perform N₂O reduction into harmless N₂,and this process can only be catalyzed by nitrous oxide reductase(N₂OR)encoded by the nosZ gene in denitrifying bacteria.At present,domestic and foreign scholars have carried out preliminary research on the N₂O microbial consumption process in paddy soil,but they are all limited to single soil.There are few studies on the difference of N₂O consumption capacity of different types of paddy soil.In this study,three typical paddy soils in subtropical region of China were selected and through laboratory culture experiment,the effects of soil type,moisture content and related functional microorganisms on soil N₂O consumption potential were systematically studied.Below are key research findings:(1)There are varying differences of soil properties,soil nutrient(NH₄⁺-N?NO₃^--N?DOC)and functional microorganism abundance existed in three types of paddy soils developed from different parent materials.However,the N₂O concentration of different types of paddy soils decreased with the increase of culture time.(2)Under the flooded and closed environment,the N₂O consumption potential of the three paddy soils was significantly different among the two treatment groups(group without exogenous N₂O added and group with exogenous N₂O added),and the total N₂O consumption showed AS1>QRC>AS2.Three types soil without N₂O added consumed 47.93%,17.87%and39.41%of N₂O respectively,indicating that the three rice soils have strong N₂O consumption capacity under experimental conditions regardless of whether exogenous N₂O is added.Besides,the three soils treated with exogenous N₂O consumed 76.3%,83.6%and 85.6%of N₂O respectively,indicating that the addition of N₂O further stimulated the N₂O consumption capacity of the three paddy soils.(3)The N₂O consumption rate of three types soil was different.The maximum N₂O consumption rate of AS1,AS2 and QRC reached 2.05,1.02,1.06?g·(kg·h)^-1,respectively.The consumption rate of AS1 is significantly higher than that in the other two soils.Soil texture,pH and organic carbon content are the main factors affecting the N₂O consumption potential of the three soils.The increase of nosZ gene abundance is also an important microbial factor driving the difference of soil N₂O consumption capacity.(4)Under the indoor condition of constant temperature,in different treatment conditions(with 20%,35%,50%and 70%water mass content)of the two treatment groups(group without exogenous N₂O added and group with exogenous N₂O added),the N₂O consumed38.30%?36.04%?44.92%?47.93%and 68.33%?66.42%?66.65%?74.1%respectively,indicating that the AS1 has a non-negligible N₂O consumption capacity both in the flooded state and in the relatively dry state,which is closely related to the higher absolute abundance of nosZ gene in soil.Exogenously added N₂O further stimulated the N₂O consumption potential of the soil,and the soil nosZ gene copy number also increased significantly.(5)There is a significant difference in the total N₂O consumption of AS1 under different water conditions.The highest moisture content(70%)was the highest consumption of N₂O in AS1.Different water treatment in the rich soil N₂O consumption rate with the increase of soil nosZ gene copy number was significantly positive correlation(P<0.01),in the two treatment groups(without added exogenous N₂O and adding exogenous N₂O group),the increase in the copy number of the nosZ gene in the AS1 with higher water content(70%)was 1.27×10⁶,2.41×10⁸copy numbers g^-1,respectively,indicating that the fluvo-aquic soil itself has strong N₂O consumption potential,and the external addition of N₂O can further stimulate the increase of functional microorganisms,so that the N₂O consumption capacity is significantly improved.