Effects Of Biogas Slurry Combined With Other Organic Materials In Lou Soil Aggregates And Soil Organic Carbon Content

As a large agricultural country,China produce a large amount of agricultural waste resources every year but the comprehensive utilization rate is low.It leads to the waste of organic resources and pollution of the environment.The application of organic materials has important functions such as improving the soil structure of farmland and enhancing soil fertility.A separate field experiment of applying biogas slurry in farmland for three consecutive years was set up to study the effect of irrigating biogas slurry on soil aggregates and soil fertility under field conditions in this research.However,different organic materials and their combined application have different effects on the stability of farmland soil aggregates and the organic carbon content.For this reason,this study selected three organic materials,biogas slurry,organic fertilizer and biochar as the research objects.Through the cultivation test,the effects of several organic materials on the stability of soil aggregates(Stability indicators such as DR_0.25,WR_0.25,DMWD,WMWD and PAD)and organic carbon content（Stability indicators such as SOC,POC and ROOC）and their differences in different application combinations at different incubation times（30,60,120and 300d）is studied.To seek the fertilization ratio which is most beneficial to the formation of soil aggregates,and the soil structure for a long time and store carbon in the soil.There are 6 kinds of treatments in the cultivation test:（1）No fertilizer treatment（CK）;（2）Single application of biogas slurry（Z1～Z6）（concentration:16.67%,20%,25%,33.33%,50%,100%）;（3）Single application of organic fertilizer（O1～O3）（concentration:1%,2%,4%）;（4）Single application of biochar（B）;（5）Combined application of biochar and biogas slurry（BZ）（6）Combined application of biochar and organic fertilizer（BO1～BO3）（concentration:1%,2%,4%）.The main results are as follows:（1）Compared with the control,the content of DR_0.25and WR_0.25in farmland soil increased by 2.92%and 98.23%,DMWD and WMWD increased by 4.76%and 42.11%,PAD reduced by 19.04%,farmland soil SOC,ROOC and POC increased by 32.80%,19.45%and 26.24%respectively after applying biogas slurry in farmland for three consecutive years.（2）When cultured to 300 days,compared with the control,WR_0.25（soil water-stable aggregates>0.25mm content）in Z1～Z6,O1～O3,B,BZ,and B01～B03 treatments increased by 70.94%～136.49%,47.92%～135.18%,31.36%,47.56%and 32.63%～114.57%respectively,PAD（soil aggregate destruction rate）decreased by 14.86%～25.09%,10.23%～28.30%,7.61%,12.96%and 5.11%～23.07%respectively.Therefore,single application of biogas slurry at the same application rate can most effectively reduce the damage rate of soil aggregates and improve the stability of soil aggregates.（3）The application of various organic materials makes the organic carbon content in the soil aggregates of various particle sizes show an increasing trend and as the size of soil aggregates increased,the organic carbon content showed an increasing trend.Compared with the control,the organic carbon content of soil>2mm aggregates increased by6.56%～120.39%,45.97%～122.82%,59.80%,55.02%,and 72.85%～142.03%in Z1～Z6,O1～O3,B,BZ,and B01～B03 treatments when they were cultured to 300 days.The organic carbon in soil micro-aggregates is relatively stable,and its content changes less during the cultivation process.At the same application rate,in improving the carbon sequestration capacity of large soil aggregates（>0.25mm）of all treatments:single application of biogas slurry>single application of organic fertilizer>biochar combined with organic fertilizer>biochar combined with biogas slurry>single application of biochar.（4）The processing of all organic materials can increase the content of SOC,POC and ROOC,and its lifting effect increases with the increase of its application rate.When cultured to 300 days,compared with the control,the SOC content in the treatments of Z1～Z6,O1～O3,B,BZ,and B01～B03 increased by 11.14%～69.54%,24.64%～55.15%,119.43%,169.68%,121.49%～263.79%,POC content increased by 1.64%～24.59%,34.43%～61.48%,28.69%,75.41%,40.16%～95.08%,ROOC content increased by0.74%～17.65%,4.41%～75.74%,5.15%,45.59%and 10.29%～82.35%.Under the same application rate,BZ treatment has the most significant effect on the improvement of SOC and POC content.The single application of organic fertilizer can greatly increase the SOC,POC and ROOC contents in the early period of cultivation（60～120d）,but show a downward trend in the later period（300d）.The above results show that the application of biogas slurry,organic fertilizer,biochar and their combined application can improve the stability of soil aggregates and increase soil organic carbon.And the higher the amount,the more significant the lifting effect.Effect in the stability of soil aggregates:single application of biogas slurry>single application of organic fertilizer>biochar combined with biogas slurry>biochar combined with organic fertilizer>single application of biochar.Regarding the carbon sequestration capacity of large soil aggregates（>0.25mm）:single application of biogas slurry>single application of organic fertilizer>biochar combined with organic fertilizer>biochar combined with biogas slurry>single application of biochar.Ability to increase soil organic carbon:biochar combined with biogas slurry>biochar combined with organic fertilizer>single application of biochar>single application of biogas slurry>single application of organic fertilizer.The effect of organic fertilizer on soil organic carbon in the early stage of cultivation is more significant,but it is weaker in the later stage.