生物炭对南方红壤和水稻土水力学特性的影响分析

The Effects of Biochar Amendment on Hydraulic Properties of Red and Paddy Soils in Southern China

【目的】揭示生物炭施加到南方典型红壤和水稻土水力特性的影响。【方法】采用高速离心机法,测定了在不同生物炭施加量(0(CK)、0.1%、0.5%、1%、3%、5%)下南方2种典型土壤(红壤和水稻土)的水分特征曲线,并运用BC模型进行拟合,探讨生物炭对土壤当量孔径分布、非饱和导水率及水分扩散度等参数的影响。【结果】随生物炭量的增加,水稻土的持水性增强,红壤的持水性则表现出先增强后减弱的趋势,在生物炭量为3%时,其持水性最强,即CK<添加量0.1%<添加量0.5%<添加量1%<添加量5%<添加量3%,且红壤的持水性整体高于水稻土;红壤的有效孔隙占比随生物炭的增加呈增大趋势,水稻土的有效孔隙占比随生物炭增加而逐渐减小;红壤和水稻土的非饱和导水率、水分扩散度均随着生物炭量的增加而降低,即CK>添加量0.1%>添加量0.5%>添加量1%>添加量3%>添加量5%,均表现出显著性差异(P<0.05),其中生物炭对红壤的非饱和导水率和水分扩散度的影响比水稻土大;红壤和水稻土的θs随炭土比的增加而增大,进气值相关参数α、形状系数n随炭土比的增加而无明显变化规律。【结论】添加生物炭能够不同程度改善水稻土和红壤的持水能力和水分运移特性。

【Background】Biochar has been widely used to improve the properties of red and paddy soils in south China,but most work focused on the chemical and biochemical properties while the change in soil physical properties due to biochar addition had been largely overlooked.【Objective】The purpose of this work is to investigate how hydraulic properties of the red and paddy soils changed following biochar amendment.【Method】Soil samples were taken from red and paddy soils amended with biochar at rate(weight/weight)of 0(CK),0.1%,0.5%,1%,3%and 5%,and their water retention curves were measured using the centrifuge method.From these water retention curves,we calculated pore-size distribution and unsaturated hydraulic conductivity of each soil sample【.Result】With biochar addition increasing,the water holding capacity of the paddy soil increased while that of the red soil increased first followed by a decline when the biochar addition exceeded 3%;on average,the water holding capacity of the red soil was higher than that of paddy soil.As the biochar addition increased,the volumetric fraction of effective pores in the red soil increased while that of the paddy soil gradually decreased.The unsaturated hydraulic conductivity and water diffusivity of both red and paddy soils decreased monotonically with the increase in biochar addition(P<0.05).Biochar addition impacted the unsaturated hydraulic conductivity and diffusivity of the red soil more significantly than on that of the paddy soil.The porosity of both red and paddy soils increased with soil carbon,while there was no noticeable change in other parameters in the van Genuchten formula used to fit the water retention curves.【Conclusion】Amending the red and paddy soil with biochar could improve their water holding capacity and hydraulic conductivity at both saturated and unsaturated conditions.