Effects Of Biochar On The Quality Of Aeolian Sandy Soil In Desert Grassland

Desertification affected by the combined action of natural and human factors,environmental pollution caused by mishandling the agricultural,forestry and animal husbandry wastes and other biomass wastes,and rising levels of greenhouse gases,which are the outstanding problem for restricting the realization of carbon peaking and carbon neutrality and improvement of human settlements.Application of biochar made by those biomasses into desert soil may be win-win strategies to solve these problems,which is in line with low carbon,green,efficient,recycle and sustainable high-quality development.Whether biochar can improve desert soil quality and reduce soil carbon emissions need to be solved.Hence,we selected the aeolian sandy soil of desert grassland as the research object,on basis of the field observation,indoor analysis and numerical simulation methods,comparatively studied the effect of biochar on the physicochemical properties and process of the soil,quantitative relationship between soil water characteristic parameters,wind erosion and nutrient,mastered the effect of biochar on the laws of soil water movement and soil respiration changes,evaluated aeolian sandy soil quality in desert grassland using biochar.It will provide technical support and theoretical basis for realizing the benign development of desert grassland ecosystem.The following conclusions were drawn:(1)Adding biochar with high dosage(4%)and small particle size(0?0.25 mm)to the soil could significantly increase soil organic matter content,specific surface area,cation exchange capacity and C/N ratio,promoted the formation of soil aggregates,and improved the stability and average geometric diameter of soil aggregates.The increasing physical stability index of the soil decreased the soil erodibility,which significantly reduced the total soil loss and salt/creep loss,and increased suspension loss and PM₁₀.Therefore,the combination of biochar with 4%dose and particle size(0?0.25 mm)should be added to the soil so as to improve the soil fertility.(2)The combination of small particle size and high dose(4%)of biochar could change the soil pore structure,significantly increased the soil total porosity,medium porosity and small porosity,hence,significantly increased soil saturated water content(0?0.25 mm,26.07%),field water capacity(0.25?1.00 mm,72.99%),wilting water content(0.25?1.00 mm,144.44%)and available water content(0?0.25 mm,65.15%).Meanwhile,soil water content with soil matrix potential<-15 Mpa significantly increased,soil infiltration rate,cumulative infiltration and water evaporation loss ratio decreased,but soil water evaporation significantly increased.Hence,the combination of biochar with 4%dose and small particle size(0?0.25 mm or 0.25?1.00 mm)was recommended to enhance soil water retention capacity.(3)Low dosage of biochar(1%)could significantly increase the soil C/N,C/P,N/P,cation exchange capacity,electric conductivity,total carbon,organic carbon,total nitrogen,total phosphorus,total potassium,alkali solution nitrogen,available phosphorus and available potassium and organic matter content.Soil temperature and respiration intensity did not significantly increase even at high biochar addition rates(4%).Therefore,biochar could be used as a measure of carbon sequestration and soil fertility improvement to control desertification land.(4)Biochar application rate,particle size and their interaction had significant effects on the soil quality,and the addition amount of biochar had the greatest effect,followed by the particle size of biochar,indicating that biochar particle size should also be regarded as an important design parameter to optimize the application of biochar.The best combination to improve the soil quality was the 4%biochar dosage and small biochar particle size(0?0.25 mm or 0.25?1 mm),the soil quality index under this combination significantly increased more than 2.5 times than the control,which was similar to the quality index of the aeolian sandy soil under the 30 years old artificial Haloxylon ammodendrum forest.(5)Soil visible/near infrared spectroscopy combined with partial least squares regression was a good way to filter out the key wavelengths of soil wind erosion indexes,water characteristic parameters,chemical properties and soil quality indexes.Pre-processing methods had significant impact on the accuracy of calibration and validation model for these indicators.Among 9 pretreatment methods,soil erodibility factor had the highest inversion accuracy using R+SG pre-processing method,soil aggregate geometric diameter,N/P,cation exchange capacity,total carbon,total nitrogen,total phosphorus,organic matter,alkalohydrolyzable nitrogen and available phosphorus contents had the highest inversion accuracy using 1/R+SG pre-processing method.The soil physical stability index,C/N,C/P and total potassium contents had the highest inversion accuracy under Log(1/R)+SG pretreatment method.The soil quality index,organic carbon,available potassium,field water capacity,wilting water content and plant available water content had the highest inversion accuracy under MA+SG+SNV pretreatment method.Soil saturated water content had the highest inversion accuracy using MA+SNV+SG+1st pretreatment method,while soil electrical conductivity had the highest inversion accuracy under MA+MSC pretreatment method.