Effect Of Biochar Addition Amount On Microbial Community Functional Diversity And CH₄,N₂O Emissions In Lou Soil

In order to investigate the effect of biochar addition on microbial biomass,microbial community functional diversity,CH₄ and N₂O emissions from Lou soil,a field plot experiment in Central Shaanxi Plain was conducted with five levels of biochar addition(0,20,40,60 and 80 t·hm^-2).The microbial biomass C,N,P,C/N,metabolic activity of microbial carbon,fluxes of CH₄ and N₂O,soil water content,soil temperature,wheat production and quality were analyzed by the chloroform fumigation-extraction,biolog-ECO plates,static chamber-gas chromatograph and other methods under application of different amounts of biochar.The main results are as follows.1.The soil microbial biomass C was increased with addition of biochar.When the biochar addition was 40–60 t·hm^-2,the soil microbial biomass C was significantly higher compared with control.When the biochar addition was equal to or above 40t·hm^-2,the soil microbial biomass C/N was significantly higher compared with control.Biochar amendment had no significant effect on soil microbial biomass N,and P.Carbohydrates and amino acids were the preferable carbon sources with high carbon utilization efficiency for soil micoorganisms.2.The metabolic activity of microbial carbon in rhizosphere soil was increased due to biochar application.When the biochar addition was equal to or above 40 t·hm^-2,the increment was significant compared with control.Biochar application had no significant effect on the metabolic activity of microbial carbon in bulk soil.Meanwhile,the richness index,Shannon-Wiener index,evenness index of microbial communities in both rhizosphere and bulk soils were not significantly affected.Biochar application enhanced the ability of soil microorganisms in rhizosphere to utilize carbohydrates,amino acids and carboxylic acids as carbon sources,while it did not significantly influence the carbon utilization ability of soil microorganisms in bulk soil.3.Compared with control,the cumulative CH₄ uptake under biochar amendment was increased by 12.88–71.61%.When the biochar addition was equal to or above 40t·hm^-2,the cumulative CH₄ uptake was significantly higher,acting like a carbon sink;and the highest uptake was at the level of 40 t·hm^-2.Biochar amendment had no significant effect on cumulative N₂O emissions and the global warming potential（GDP）.The greenhouse gas intensity（GHGI）was decreased by 13.24–22.14%.The wheat yield was increased by 1.72–32.19%after biochar addition.When the applied biochar level was equal to or above 40 t·hm^-2,the wheat yield increments were significant.The soil organic carbon and water content under biochar amendment was increased by 1.42–2.69 times and 7.08–11.96%,respectively.The results suggested that Lou soil was the sink of CH₄ and the source of N₂O during the winter wheat growth period.4.The water content,flour yield,test weight and dough development time of winter wheat grain were increased,while the sedimentation value was decreased under the biochar amendment.Biochar application had no significant effects on water absorption,starch content,crude protein（dry basis）content,gluten（wet basis）content of winter wheat grain,dough stability time and maximum dough resistance.Based on the above analyses,biochar addition of 40 t·hm^-2 was the most suitable application amount for the Lou soil in the current study.