Effects Of Biochar On Soil Organic Carbon Composition And Microbial Activity

Biochar have been considered as a powerful tool for carbon sequestration and greenhouse gas mitigation as a new soil amendment.In recent years,with the increasing study interest in the application of biochar in agriculture,the focus of its research have shifted to promoting soil water conservation,improving soil fertility and crop growth.In this study,a long field experiment was conducted using a winter wheat and summer maize rotation system in Shanxi province,China.The biochar was mixed with 0,5,10,15 and 20 t·ha^-1?B0,B5,B10,B15,B20?into the topsoil?0²0 cm?by field positioning test.Biochar was first applied in October2011,and every treatments were repeated applyying in October 2016 according to the aforementioned application amount.This study began with the 2016 winter wheat season,and analyzed the effects of biochar on the physical structure,water holding capacity,total nitrogen,ammonium nitrate nitrogen,total organic carbon,carbon components,enzyme activity,microbial abundance,crop yield and yield components of loess soil.The interaction among soil physical and chemical properties,organic carbon components and microbial abundance after biochar application was studied.The main results were as follows:?1?Biochar can significantly reduce soil bulk density,increase soil total porosity,capillary porosity,saturated water content and field water holding capacity.Biochar has a certain effect on soil water content under the higner application.In the seedling stage,jointing stage,silking stage and maturity stage of summer maize in 2017,the soil moisture content of B20 treatment was 14.78%,14.61%,13.58%and 13.66%higher than that of B0 treatment,respectively.?2?Biochar can increase the total nitrogen content of soil in the more the amount of biochar applied.At the seedling stage of winter wheat and summer maize,biochar could significantly increase the content of nitrate and ammonium nitrogen in soil.After jointing stage,the contents of nitrate nitrogen and ammonium nitrogen in soil were lower,but there was no significant difference between treatments.Soil pH didn't differ significantly among treatments,and biochar had no significant effect on soil pH.?3?Soil total organic carbon,active organic carbon,highly active organic carbon and particulate organic carbon content increased with the increase of biochar addition.In a word,B20 treatment performed best,and in the mature period of summer maize in 2017,the total organic carbon,the active organic carbon,the highly active organic carbon and the particulate organic carbon was 60.17%,71.97%,78.96%and 35.44%higher than that of B0 treatment.Biochar also significantly increased soil carbon pool index and carbon pool management index.The correlation analysis showed that there were significant correlations between total organic carbon,carbon components and soil total nitrogen,ammonium nitrate nitrogen and other physical and chemical properties.?4?Biochar treatment significantly increased soil urease and catalase activity,but had no significant effect on invertase activity.Biochar significantly affected the number of gene copies of bacteria,AOA,AOB,nirK and nirS,and the higher the amount of biochar applied,the higher the number of gene copies.At silking stage of summer maize,16S rRNA gene copies treated with B20 were 1.39 times higher than B0,AOA gene copies were 70.35%higher than B0,AOB gene copies were 31.26%higher than B0,nirK gene copies were 48.68%higher than B0,and nirS copies were 53.93%higher than B0.The results of correlation analysis showed that the physical and chemical properties of soil were highly correlated with microbial activity.Principal component analysis showed that the comprehensive scores of PC1 with different treatments were B20>B15>B10>B5>B0,indicating that the effects of biochar addition on soil physical and chemical properties and microbial abundance were significant.?5?Biochar also had significant effects on the yield of winter wheat and summer maize.In terms of yield components,biochar mainly increased the number of spikes per unit area of winter wheat,the number of grains per spike and grain weight of summer maize;the best yield-increasing effect of each treatment was 20 t·hm^-2 application rate,and the average yield-increasing range of winter wheat and summer maize was 16.48%and 33.97%respectively in two-year experiment.Generally speaking,the application of biochar can significantly improve soil physical structure and soil physical and chemical properties,increase soil organic carbon pool and the content of carbon components,improve soil enzyme activity and microbial abundance,and also promote crop agronomic characteristics and yield.Under the condition of this experiment,the treatment effect of 20 t·ha^-1 is the best,which has a certain popularization prospect.