The Impact Of Modified Biochar On Soil Phosphorus Fractionation,enzymatic Activity And Greenhouse Gases Emission Under Different Acidic Soils

Biochar is a material prepared from the different feedstocks.The preparation of biochar on one hand solves the problem of waste disposal,while on the other hand biochar is alkaline material increased the p H of acidic soils and reduced the environmental pollution.The acidic soils are deficient in phosphorus and have high greenhouse gas emissions（GHG）.Therefore,in this study we applied Magnesium-modified（Mg-BC）and non-modified wheat straw biochar（BC）to red and black soil,and investigated its effect on the physiochemical properties,phosphorus fractions,microbial community structure and greenhouse gas emissions under both red and black soils.The main results of the studies are as under.（1）This study was an incubation study,in which we selected two different soils namely,S1:Qiyang red soil and S2:Harbin black soil,and applied two different types of biochar such as BC and Mg-BC of wheat straw.To investigate the effect of both biochar on soil biochemical properties and P fraction we conducted a 90 days incubation experiment.The study includes five treatments,without amendments control（CK）,two levels of BC(1%and 2.5%or 10 and 25 g kg^-1soil)and two levels of Mg-BC(1%and2.5%or 10 and 25 g kg^-1soil).The biochar amendments significantly increased the physiochemical properties（AP,AK,SOC and p H）under both soils as compared to CK.The concentration of MBC,MBN and MBP were increased by 4-10%,14-40%,18-38 in S1,while 1.8-7%,22-40%and 25-41%in S2,in both BC and Mg-BC biochar addition respectively.The acidic phosphatase increased at 1%of BC and Mg-BC but decreased at 2.5%rate,while the alkaline phosphatase and catalase enzymes significantly increased by both biochars irrespective of soil types.Furthermore,BC and Mg-BC significantly increased the concentration of labile-P and Dil-HCl-P.The resin-P was increased by 28-52%and 8-20%,Na HCO₃-Pi was increased 22-41%and 20-39%and Dil-HCl-P was increased by 11-32%and 11-34%in S1 and S2soils respectively,in comparison to CK.While,the Na HCO₃-Po and Con-HCl-Po showed no significant results.The moderately labile,non-labile and residual-P were decreased as the rate of BC and Mg-BC was increased.In S1 and S2soil,Na OH-Pi was decreased by 12-36%and 19-46%,Na OH-Po was decreased by6-64%and 3-66%,Con-HCl-Pi was decreased by 20-58%and 8-36%and residual-P decreased by 60-76%and 29-100%in comparison to control.To further elaborate our results,we perform PLS-PM analysis which showed that the amendment of modified biochar under both S1 and S2 revealed significantly positive direct effect on phosphorus availability and phosphorus fractions.（2）A 90 days incubation experiment was conducted to investigate the effect of non-modified and modified biochar on soil physiochemical properties,microbial structure,enzymatic activities and greenhouse gases emissions（GHG）under two different soils:QY1:Qiyang control（CK）treatment（p H=5.7）and QY2:Qiyang NPK treatment from the long-term experimental field（p H=4.4）.The study composed of five treatments（each soil has five treatments）having three replications.The treatments include,without biochar addition,control（CK）,two levels of BC:BC₁(1%w/w or 10 g kg^-1soil),BC_2.5(2.5%w/w or 25 g kg^-1soil)and two levels of Mg-BC:Mg-BC₁(1%w/w or 10 g kg^-1soil),Mg-BC_2.5(2.5%w/w or 25 g kg^-1soil).The results showed that both biochars significantly improved the physiochemical properties under both soils.The gram positive and negative bacteria,actinomycetes and total PLFA concentration was significantly increased after the addition BC and Mg-BC but decreased the concentration of fungi in QY1 and QY2 soils.In case of AMF in QY1 it displayed no significant results while in QY2 it showed slightly significant results.The urease and invertase activity were increased by 25-49%and 27-53%in QY1 and 5-11%and 8-16%was increased in QY2.The activity ofβ-glucosidase and dehydrogenase were decreased by 20-71%and 10-63%and 22-100%and 13-58%in QY1 and QY2 soils respectively.The cumulative CO₂emission increased by 62.79%,56.32%,63.33%,and 54.22%for BC₁,Mg-BC₁,BC_2.5and Mg-BC_2.5in QY1 while CO₂cumulative emission was increased by 37%,27%,35%,and 24%for BC_1,Mg-BC₁,BC_2.5and Mg-BC_2.5in QY2 soil.The CH₄cumulative emission was increased with biochar addition,but showed non-significant results within the treatments under both soils.The cumulative N₂O was significantly decreased by biochar addition and the decreased is more dominant when the rate of biochar increased.The mean cumulative N₂O emission was decreased by 18-32%and 17-62%for QY1 and QY2 soil.（3）Finally,the current study investigated the effect of Mg-modified and non-modified biochar on phosphorus fractionations and GHG emissions combinedly.The soil was amended with two types of wheat straw biochar namely,Mg-BC and BC at the rate of 1%and 2.5%（w/w）and control without biochar.The results showed that Mg-BC and BC improved the physiochemical properties of acidic black soil.The Mg-BC and BC increased the activity of urease,phosphatase and catalase by 27–48%,22–28%and 12–21%,respectively as compared to control.Both biochars were significantly increased the resin-P,Na HCO₃-Pi and HCl-P by 35–56%,32–58%and 18–38%,respectively,while decreased the concentration of Na OH-P and residual-P compared to control.The cumulative CO₂emission was significantly increased by both Mg-BC and BC,but Mg-BC decreased the CO₂emission by 5–13%when compared to BC.The N₂O cumulative emission was significantly reduced by and 17–44%in Mg-BC and 11–29%,in BC respectively,compared to control.The RDA results also showed that increase in labile P fraction could decrease the emission of GHG.These results suggested that Mg-BC and BC significantly reduced the acidification and GHG emissions in acidic black soil and increased the labile-P fraction and its availability for the plant.From this study it was revealed that Mg-BC biochar into acidic soil significantly increased the phosphorus availability,enhanced microbial community and mitigate the emissions of greenhouse gases.Furthermore,the acidic soils have the deficiency of Mg which could also be improved after the application of Mg-modified biochar.Moreover,the labile P fractions also showed negative relationship with N₂O emissions which means that increasing in P availability the N₂O emission would be decreased.