Positioning Study On Soil Ecological Effect Of Biochar In The Semi-arid Area

The poor structural and the lower capacity to retain water and nutrients of soils in theLoess Plateau, restrict the sustainable development of agriculture and ecological restoration.Direct incineration of the crop residues and the chemical fertilizers abuse, provide animportant source of greenhouse gas emission. Greenhouse gas emission caused an increasingglobal warming, resulting in a series of environmental problems, including desertification, sealevel rise and intensified hurricanes, which are the major challenges the Global is facing today.The potential of biochar to improve soil properties and mitigate climate change, is expected toprovide a new way for the integrated treatment of agricultural waste, has importantsignificance for the Loess Plateau soil quality improvement and the living environmentremediation.A field experiment based on the long-term in-situ experiments was conducted toinvestigate the biochar amendment on soil physical and chemical properties, water-holdingcapacity and emission of greenhouse gases （CO₂, CH₄,N2O） after6months. The treatmentincluded two types of biochars （sawdust-derived biochar anb locust tree skin-derived biochar）and four addition ratios （0%,1%,3%,5%, W/W）. The main conclusions are as follows:1) After6months, the effect of biochar on soil physical and chemical properties wasobserved. The study found that both of the sawdust biochar and the locust tree skin biocharchanged the soil physical and chemical properties. Biochar can reduce soil bulk density,increase soil pH, electrical conductivity, cation exchange capacity, organic matter and totalnitrogen content. The locust tree skin biochar had a significant effect than sawdust biochar,and high biochar application ratio effected significantly than the low dosage. The effect of thesame level biochar amendment on soil cation exchange capacity was significantly different.2) The effect of biochar addition on soil water retention characteristics was studied onthe base of the plot experiment. The results showed that biochar amendment can improve fieldcapacity and soil water-holding capacity, reduce the soil infiltration capability. The fieldcapacity increased with the amount of biochar, but soil saturated hydraulic conductivitydecreased with the increase of biochar. With the increase of soil depth, soil moisture contentincreased firstly and then decreased in the0-200cm depth range, and the highest contentappeared at60cm depth. The locust tree biochar has a significant effect than sawdust biochar.Using van Genuchten model to simulate soil water-holding characteristics after the biochar addition, the correlation coefficient reached a significant level.3) The Li-8100and gas chromatography were used to monitor the effect of biocharaddition on soil greenhouse gas emissions. The research found that biochar addition canincrease soil CO₂flux, inhibit soil CH₄emissions, but there is no apparent regularity on soilN₂O emissions. Soil surface CO₂flux with biochar addition showed an increasing trend, butno significant difference existed. The inhibitory effect of biochar addition on soil CH₄emissions increased with the increasing of the biochar addition. But sawdust biochartreatment was just significantly different at5%dosage, and the locust tree biochar treatmentexisted significant difference when the addition level reached at3%and5%additionproportion.