Effects Of Biogas Slurry And Biochar On Soil Aggregate Organic Carbon And Microbial Community Diversity

Global change and the reasonable use of biogas slurry were important challenges we faced.In this study,we examined the effects of different concentration levels of biogas slurry and biochar on the stability and carbon sequestration capacity of soil aggregates,and sought a reasonable management method to increase soil organic carbon pool for mitigating the greenhouse effect.A nested design was adopted in the poplar plantation in the northern Jiangsu Province,and four biogas slurry application levels were set up,which were CK(0 m³·hm^-2·a^-1),L(125 m³·hm^-2·a^-1),M(250 m³·hm^-2·a^-1),H(375 m³·hm^-2·a^-1),respectively,and the four biochar application levels were CK(0 t·hm^-2),L(40 t·hm^-2),M(80 t·hm^-2),H(120 t·hm^-2),respectively.The changes of soil aggregate size,TOC content and microbial diversity under different concentrations of biogas slurry and biochar application levels were the main research priorities.The results showed that:?1?Application of biogas slurry significantly decreased soil pH,C/N ratio and soil bulk density.Application of biochar significantly increased soil pH and significantly reduced soil bulk density.Biochar can moderate the decrease of soil pH caused by biogas slurry to some extent.Both increased soil TOC content,but the soil had limited ability to fix TOC and there was carbon sequestration.?2?L and M treatments of biogas slurry significantly increased the content of large macroaggregates?>2mm?,and H treatment significantly increased the TOC content of small macroaggregates?0.25-2mm?.TOC was mainly stored in microaggregates?<0.25mm?.With the increased of TOC input,TOC was mainly stored in small macroaggregates?0.25-2mm?.?3?L treatment and M treatment of biogas slurry significantly increased the MWD.H treatment of biogas slurry had weakened the increase of large macroaggregates?>2mm?content and MWD,which was not conducive to the improvement of soil aggregate stability.?4?Combined application of M treatment of biogas slurry and biochar,the large macroaggregates?>2mm?content and its TOC storage,soil agglomerate MWD reached the peak.?5?Application of biogas slurry decreased the fungal diversity of aggregates.Combined application of L treatment of biogas slurry and M treatment of biochar increased bacterial diversity of soil aggregates,increased fungal diversity of macroaggregates?>2mm?and microaggregates?<0.25mm?,and increased the number and abundance of fungal subdominant in small macroaggregates?0.25-2mm?.In short,L and M treatment of biogas slurry significantly increased the content of large macroaggregates?>2mm?and the stability of soil aggregates.H treatment mode of biogas slurry significantly increased the ability of carbon sequestration in small macroaggregates?0.25-2mm?.Our results suggested that TOC fixation was in small size before large size.Combined application of M treatment of biogas slurry and biochar significantly increased the content and the ability carbon sequestration ability of macroaggregates?>2mm?and was beneficial to the stability of aggregates.Combined application of L treatment mode of biogas slurry and M treatment of biochar was beneficial to the improvement of soil microbial diversity.