Effect Of Biochar On The Infiltration And The Profile Moisture Dynamics Of Purple Soil

Purple soil is one of the most important soil types in China,its mineral nutrient content is sufficient and it is fertile dry tillage soil,but the soil has been seriously eroded in recent years,which is a threat to China's food security and sustainable agricultural development.The application of biochar from agricultural waste such as crop straws into the soil can not only repair and improve the soil,but also solve the problems of resource waste and environmental pollution,which has important application value for food security,energy security and environmental protection.Biochar can reduce soil hardness,increase organic matter content,improve soil structure,improve soil infiltration capacity and water holding capacity,and it may directly or indirectly affect the movement and retention of water in the soil,therefore,it is of great significance to study the dynamic changes of soil infiltration and soil profile moisture dynamics after biochar application.Most of the existing studies on the effect of biochar on soil water movement are focused on the black soil area and the yellow soil area,and most of them focus on the effect of biochar additive amount,and there is little discussion on the two factors of biochar particle diameter and biochar added depth.Studies on the water infiltration of purple soil are mostly focused on the pure purple soil or the mixture of soil and stone under different land use types.The research on the water improvement of purple soil is mainly focused on the aspects such as mulching and straw mulching,while the research on the water infiltration of purple soil under the action of biochar is rare.In this paper,the biochar in different applied amount,particle diameter and added depth,the indoor one dimensional vertical constant head method is adopted to carry out the soil infiltration test and determination of the soil moisture dynamic change,aiming to reveal the purple soil water infiltration characteristics and profile moisture dynamic variation law,comparative evaluation of the applicability of Kostiakov model and Horton model.It can provide scientific basis for flood discharge and drought resistance in agricultural production and efficient utilization of agricultural soil and water resources in purple soil area,and it has important practical significance and practical value for reducing soil erosion in cultivated land,preventing agricultural non-point source pollution,improving soil water holding capacity,reducing loss from natural disasters and increasing production yield.The study found that:?1?Under the premise of biochar particle diameter 0.25-0.5mm,the applied amount of biochar to purple soil can inhibit soil water infiltration to a certain extent.The average infiltration rate decreased with the increase of biochar applied amount,and increased with the increase of biochar particle diameter.The cumulative infiltration amount was the maximum when the biochar was applied at 3%,the particle diameter was 0.25-0.5mm,and the applied depth was 10-20cm.The cumulative infiltration amount increased by 35.14%,35.14%and 13.07%,respectively.?2?The migration depth of the wetting front was proportional to the square root of the infiltration time(t^0.5).Under the premise of biochar particle diameter 0.25-0.5mm,the applied amount of biochar to purple soil can inhibit the wetting front migration to a certain extent.The average migration rate of the wetting front decreased with the increase of the biochar,and reached13.14cm/h faster when the biochar particle diameter was 0.5-1mm.When biochar was applied at a depth of 10-20cm,the inhibition of wetting front propulsion was the weakest,and the strongest at a depth of 20-30cm.?3?The applied amount of biochar to the soil can significantly affect the dynamic change of water in the soil profile after the end of infiltration of purple soil,and then affect the water distribution in each period.Biochar can significantly increase the water holding capacity of purple soil.The water holding capacity of the soil was the best when the biochar is applied at 5%and particle diameter is 0.5-1mm within 24 hours,and the water holding capacity of the soil is the best when the biochar is applied at 3%and particle diameter is 0.25-0.5mm within 72 hours,and the water content of the overall profile of the biochar in the 10-20cm soil layer can stay at a high level for a long time under test conditions.?4?The infiltration rate varied with time according to the power function under the conditions of different biochar application amounts,particle diameters and application positions.Compared with the Horton model,the Kostiakov model was more suitable for predicting the infiltration process of purple soil after the application of biochar.