Impact Of Biochar On Adsorbed Properties Of Inorganic Nitrogen,Seedling Development And Soil Microbes

Biochar is a type of carbon-rich,light-weight,porous solid material produced by high-temperature anaerobic digestion of biomass such as straw,fruit hulls,and sawdust.It has a large specific surface area,strong adsorption capacity,high thermal and chemical stability,surface including varieties of organic functional groups,metal ions and so on.This was excellent potential in terms of fluffy soil,maintained soil moisture,controlled soil nutrient loss,and promoted crop growth on farmland.However,the property of biochar was affected by factors such as the preparation of raw materials,pyrolysis process and application conditions.In this study,raw materials were peanut shell,corn stalks,aspen chips and bamboo chips,batch adsorption experiments were set up and combined with indoor cultivated test,studied on the adsorption of different biochar on ammonium nitrogen and nitrate nitrogen,observed the germination of crop seeds,the response characteristics of seedling development and soil microorganisms to biochar input,revealed the mechanism of biochar on soil nitrogen activity and evaluated safety to farmland application.To provided theoretical support for the optimal development of biochar.The main findings were as follows:（1）The adsorption of NH₄⁺-N/NO₃^--N by biochar was affected by pH.With the increase of pH value,biochar’s adsorption of NH₄⁺-N increased,however,the adsorption of NO₃^--N decreased significantly.Absorption of NH₄⁺-N/NO₃^--N on biochar in equilibrium with800mg·L^-1,the maximum adsorption capacity for NH₄⁺-N was 9.5¹2.5mg·g^-1,the adsorption capacity was the peanut shell（PBC）>the corn stalks（MBC）>the aspen chips（BBC）>the bamboo chips（ABC）,the Langmuir model could described the thermodynamic behavior of biochar,the pseudo-second-order kinetic equation could described the dynamic adsorption process of biochar on NH₄⁺-N and the adsorption reached the equilibrium within 50min;the maximum adsorption capacity for NO₃^--N was 18⁴4mg·g^-1,the adsorption capacity was MBC>PBC>BBC>ABC,PBC,MBC and BBC adsorption isotherm conformed to the Langmuir model,ABC accorded with the Freundlich model,adsorption reached equilibrium within 60min,the pseudo first-order kinetic equation could described the dynamic adsorption process of biochar on NO₃^--N.（2）The four kinds of biochars were alkaline,a range of 8.76⁹.92,a porosity of0.89⁴.77nm,oxygen-containing functional groups such as-O-,-OH,and-C=O,and ash inclued N,S,K and other nutritive elements..Polycyclic aromatic hydrocarbons（PAHs）were detected in the biochar extracts and after application,in the range of 62.47-93.55μg·kg^-1.There was significant difference in the PAHs content of different biochar.Compared with the control,the biochar had no significant effect on the percentage of germination of wheat and cucumber seeds,but with the increase of the amount of biochar added,the root length and shoot length of the crop showed obvious first increase and then decrease trend,the addition amount is less than PBC 80.0g·kg^-1,the addition of MBC,ABC and BBC were lower than40.0g·kg^-1 respectively,the promotion of wheat root length and shoot length was PBC>MBC>ABC>BBC;cucumber root length promotion performance ABC>PBC>MBC>BBC,shoot length showed PBC>ABC>BBC>MBC.Biochar of high addition(>160.0g·kg^-1)showed significant inhibitory effects,the inhibition rate of wheat was 110.22 to 4.89%,the cucumber was 82.56 to 4.17%.the most significant inhibition rate is MBC.（3）The application of PBC,MBC and ABC increased the total phospholipid fatty acids（PLFAs）content in soil,which was increased by 17.48,15.44,and 9.54nmol·g^-1,respectively,compared with the control(24.05nmol·g^-1).The increase was PBC>MBC>ABC,but with the increase in the amount showed a downward trend.The addition of BBC significantly reduced the total amount of PLFAs in the soil and the decrease ranged from 12.38 to 9.33nmol·g^-1.Four kinds of biochar added significantly increased the soil fungal/bacterial ratio.The MBC and ABC increased the amount of fungi,which was 29.4%-82.6%higher than CK.High amounts(160g·kg^-1)of PBC,BBC significantly reduced the amount of fungi lower than CK to51.0%-82.6%.PBC,MBC and ABC additions(20.0⁴0.0g·kg^-1)increased the amount of soil bacteria,while high-level additions(160g·kg^-1)decreased.Added BBC,soil bacteria decreased by 45.7%⁷6.2%.There was a negative correlation between the amount of soil bacteria and pH after PBC,MBC and ABC addition.The MBC and ABC reached significant levels,and the fungus had a positive correlation with EC,among which MBC reached a significant level（r=0.595）.There was a significant negative correlation between soil bacteria and NH₄⁺-N content added by PBC,and there was a significant negative correlation between MBC added soil fungi/bacteria and NH₄⁺-N content.Added BBC,soil gram-negative bacteria was significantly negatively correlated with NH₄⁺-N content.It can be seen that the addition of biochar affects soil microbial community structure by regulating soil pH,EC and NH₄⁺-N content.