Study On The Regulatory Effects Of Biochar And Water Conditions On Carbon Sequestration And Emission Reduction In Different Saline Soils

The massive emission of greenhouse gases is a common concern,and farmland soil is the main source of N₂O and CO₂ emissions.In order to better clarify the emission process of N₂O and CO₂ in different saline-alkali soils and possible regulatory pathways,this study used indoor culture to select three different texture soil types（silty loam,silty clay and sandy loam）.Five salinization levels（Na:Ca:Mg=2:1:1）（S0,S1,S2,S3 and S4:the amount of salt added was 0%,0.25%,0.5%,0.75%and 1%of soil quality,respectively）and two biochar addition methods（B0:no addition;B1:the addition amount was 5%of the soil mass）and two water conditions（W0:60%field capacity;W1:100%field capacity）,soil N₂O and CO₂ emission processes were monitored,and soil electrical conductivity(EC_1:5),p H,soil mineral nitrogen（NH₄⁺-N and NO₃^--N）and soil organic carbon（TOC）were measured.The effects of water conditions and biochar addition on N₂O and CO₂ emissions from saline-alkali soils with different textures were studied to provide a theoretical basis and technical approach for carbon sequestration and emission reduction in saline-alkali soils.The main results are as follows:（1）The addition of salt in silty loam can effectively reduce the emission of N₂O and CO₂.The moisture content has a significant effect on the emission of N₂O and CO₂.The addition of single biochar can reduce the cumulative emission of CO₂,but has no significant effect on N₂O emission.Under the treatment of no biochar（B0）,the N₂O emission of W1 increased by3%,84.8%,187.3%,729.7%and 306.3%,respectively,compared with W0 under different salt conditions.Under the treatment of adding biochar（B1）,the N₂O emissions of W1 increased by 12.6%,18.1%,317.7%,596.9%and 591.3%respectively compared with W0 under different salt conditions.In the case of S3 treatment,the increase of N₂O emission was the largest,and the addition of biochar could reduce the increase of N₂O emission.Under the treatment without biochar（B0）,the CO₂ emission of S2W1 was 6.0%lower than that of S2W0.Except for S2,the CO₂ emission of W1 was 26.7%,26.2%,254.1%and 72.0%higher than that of W0.Under the treatment of adding biochar（B1）,the CO₂ emission of W1 increased by32.1%,73.9%,19.0%,184.7%and 120.1%respectively compared with W0 under different salt conditions.In the case of S3 treatment,the increase of CO₂ emission is the largest,and the addition of biochar can reduce the increase of CO₂ emission.（2）Adding salt to silt clay can effectively inhibit soil N₂O and CO₂ emissions.Soil moisture content had a significant effect on N₂O and CO₂ emissions,and rainfall significantly increased N₂O and CO₂ emissions.The effect of biochar addition on N₂O and CO₂ emissions is inconsistent.Single biochar addition can effectively reduce the impact of cumulative CO₂emissions,but has no significant effect on N₂O emissions.Under the condition of no biochar（B0）,the N₂O emissions of W1 increased by 5.4%,220.2%,777.0%,33.6%and 8.0%,respectively,compared with W0 under different salt conditions.Under the treatment of adding biochar（B1）,the N₂O emission of W1 increased by 27.4%,257.1%,580.5%,51.5%and 1.6%respectively compared with W0 under different salt conditions.In the case of S2 treatment,the increase of N₂O emission was the largest,and the addition of biochar could reduce the increase of N₂O emission.Under the treatment without biochar（B0）,the CO₂ emissions of W1 increased by 39.1%,58.3%,98.7%,60.4%and 38.3%,respectively,compared with W0under different salt conditions.Under the treatment of adding biochar（B1）,the CO₂ emission of W1 increased by 29.8%,57.2%,98.6%,55.3%and 20.5%respectively compared with W0under different salt conditions.In the case of S2 treatment,the increase of CO₂ emission is the largest,and the addition of biochar can reduce the increase of CO₂ emission.（3）In sandy loam soil,the higher the salt content,the lower the cumulative emissions of N₂O and CO₂,and salt can effectively inhibit soil N₂O and CO₂ emissions.Soil moisture content had a significant effect on N₂O and CO₂ emissions,and rainfall significantly increased N₂O and CO₂ emissions.Biochar addition had no significant effect on N₂O and CO₂ emissions.Under the treatment of no biochar（B0）,the N₂O emissions of W1 increased by 30.7%,363.1%,2.7%,0.2%and 0.1%,respectively,compared with W0 under different salt conditions.Under the addition of biochar（B1）,the N₂O emissions of W1 increased by 75.5%,320.9%,2.8%,1.4%and 1.8%,respectively,compared with W0 under different salt conditions.In the case of S1 treatment,the increase of N₂O emission was the largest,and the addition of biochar could reduce the increase of N₂O emission.Under the treatment without biochar（B0）,the CO₂emissions of W1 increased by 40.9%,60.4%,3.5%,10.0%and 1.3%,respectively,compared with W0 under different salt conditions.Under the treatment of adding biochar（B1）,the CO₂emission of W1 increased by 64.1%,66.8%,5.0%,12.4%and 5.7%respectively compared with W0 under different salt conditions.In the case of S1 treatment,the increase of CO₂emission was the largest,and the addition of biochar could reduce the increase of CO₂ emission.（4）The contents of NH₄⁺-N and NO₃^--N in three soils were different.The difference of NH₄⁺-N in silty loam was positive,and the difference of NO₃^--N was negative.The difference of NH₄⁺-N in silty clay and sandy loam was negative,and the difference of NO₃^--N was positive.The nitrogen transformation process of different texture soils is different.The silt loam is dominated by denitrification,and the silt clay and sandy loam are dominated by nitrification.Salt and water treatments can effectively control N₂O and CO₂ emissions.Relatively speaking,water plays a leading role in N₂O and CO₂ emissions.Different types of soil have different sensitivity to salt content.Sandy loam is more sensitive to salt than silty loam and silty clay.The response of N₂O and CO₂ emissions to salt is more sensitive,and biochar addition has a large difference for different types.Therefore,water and salt have certain significance for soil carbon sequestration and emission reduction,but the effect of biochar addition on soil carbon sequestration and emission reduction should be considered comprehensively.