Conditioning Effect Of Sludge Biochar On Soil Physicochemical Properties

As a new type of environmental functional material with ecological remediation function,sludge biochar has a wide application prospects in soil improvement.To tackle the problems of low fertility,sticky weight and weak fertilization capacity of acid soil in Yunnan,three types of sludge biochars,including municipal sludge(SZ),pharmaceutical sludge(YC)and chicken manure(JF),prepared by pyrolysis at 400 ℃and 600 ℃,were applied into common soil and acid soil at the amount of 1% and 2%,respectively,for soil cultivation experiments of 42 days.13 treatments were set up,namely,the control group(CK),1%-SZ400、1%-SZ600、1%-YC400、1%-YC600、1%-JF400 、 1%-JF600 、 2%-SZ400 、 2%-SZ600 、 2%-YC400 、 2%-YC600 、 2%-JF400、2%-JF600,to investigate the effects of biochar on the physical and chemical properties,nutrient content and aggagreates of acid soil and common soil.The work will provide theoretical basis and practical guidance for land application of sludge bichars.The main findings are as follows:(1)Different sources and pyrolysis preparation temperatures have significant effects on the elemental and structural characteristics of municipal sludge biochar(SZBC),pharmaceutical sludge biochar(YCBC)and chicken manure biochar(JFBC).With the increase of pyrolysis temperature,the contents and yields of C,H,O and N in SZBC,YCBC and JFBC decreased,while the ash content increased.At the same pyrolysis temperature,C and N contents of JFBC were higher than those of SZBC and YCBC,but ash contents of SZBC and YCBC were higher than those of JFBC.The contents of Fe and Zn in SZBC,Ca in YCBC and K,Ca,P and Mn in JFBC were the highest.(2)Biochars can increase the p H and CEC of common and acid soils,and increase the contents of TOC,TN,AN,AK,AP etc.In a word,the improvement effect of JFBC is better than that of SZBC and YCBC.(3)Adding SZBC,YCBC and JFBC can increase the contents of Fe,Mn and Zn in common soils,but had no significant effect on the contents of Cu,Cr,Ni and Pb.In acid soils,the addition of SZBC,YCBC and JFBC increased the contents of Fe and Zn to some extent and decreased the contents of Mn,but had no significant effect on the contents of Cr,Ni and Pb.(4)All three types of biochar application reduced the content of mechanical macroaggregates in common soil,but the effects of pyrolysis preparation temperature and application rate of the three types of biochar on the content of mechanical macro aggregates in acidic soil were significantly different.under JFBC treatment,the low rate of application promoted the accumulation of the content of mechanical macroaggregates in acidic soil,while the high rate of application had a dispersing effect on mechanical macroaggregates.This indicates that the application of high rate of JFBC increased the friability of acidic soil and improved the structure of acidic soil.under YCBC treatment,biochar prepared by low-temperature pyrolysis promoted the accumulation of mechanical macroaggregates content more than that prepared by high-temperature pyrolysis,because YCBC prepared by low-temperature contained higher organic matter content and richer functional group structure,which better promoted the agglomeration of soil particles.SZBC The effects of different pyrolysis temperatures and application rates on the content of mechanical aggregates in acidic soils under the treatment were different,mainly because the formation and stability of aggregates were influenced by a combination of multiple factors.(5)The application of three types of biochar promoted the accumulation of waterstable macroaggregates and enhanced the stability of aggregates in common and acidic soils,but there were differences in the effects of biochar in the two soils.In the common soil,the increase of aggregates stability was ranked as JFBC>SZBC≈YCBC;in the acidic soil,the increase of aggregates stability was ranked as YCBC>JFBC>SZBC.(6)There were significant differences in the effects of the three biochar additions on the relative abundance of soil functional groups.For common soils,the application of SZBC reduced the relative abundance of-CH and C=C functional groups of whole soil organic matter,but had no significant effect on the relative abundance of C-O functional groups;the application of JFBC and YCBC increased the relative abundance of C=C and C-O functional groups of whole soil organic matter,and reduced the relative abundance of-OH and-CH functional groups.For acidic soils,SZBC application decreased the relative abundance of-OH,-CH,C=C and C-O of whole-soil organic matter;YCBC application increased the relative abundance of-CH and C-O and decreased the relative abundance of-OH and C=C of whole soil organic matter;JFBC application increased the relative abundance of C=C and C-O functional groups of whole-soil organic matter and decreased the relative abundance of-OH and-CH functional groups and decreased the relative abundance of-OH and-CH functional groups.(7)The addition of the three biochars significantly increased the light group content and decreased the mineralogically bound recombination content for both common and acidic soils,but there were differences in the content of calcium-bound organic carbon(Ca-SOC)and iron-aluminum-bound organic carbon(Fe/Al-SOC)in recombination.For common soils,the application of the three biochar species increased the Ca-SOC content and Fe/Al-SOC content in whole soils and at different grain classes.For acidic soils,the application of the three biochars increased the whole soil and Fe/Al-SOC contents at different grain levels,and the Ca-SOC contents increased by 44.0% and 33.3% under YCBC and JFBC treatments,respectively,but SZBC had no significant effect on the CaSOC contents.(8)The correlation results showed that all three biochar applications essentially promoted the formation of organic-inorganic complexes in both normal and acidic soils,but the types of effects differed.For common soil: SZBC application promoted the formation of aromatic carbon-Fe/Al complex,YCBC application promoted the formation of O-alkyl carbon-Fe/Al complex,and JFBC application accumulated the content of amorphous Fe-Si-Al colloids and aromatic carbon-O-alkyl carbon-Fe/Al complex.For acidic soils: SZBC application promoted the formation of O-alkyl carbonCa complex and partially amorphous Fe-Al-Si colloids,YCBC promoted the formation of O-alkyl carbon-Ca complex,and JFBC promoted the formation of O-alkyl carbonaromatic carbon-Ca/Fe/Al complex and partially amorphous Fe-Si-Al colloids to different degrees to improve the agglomerate stability.