Effects of Bacillus Subtilis on Water Movement and Water Stable Aggregate in Saline Alkali Soil
HOU Yaling;ZHOU Beibei;WANG Quanjiu;CHEN Xiaopeng;TAO Wanghai;ZHANG Jihong;State Key Laboratory Base of Eco-hydraulic Engineering in Arid Area,Xi'an University of Technology;State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau,Institute of Soil and Water Conservation,Chinese Academy of Science and Ministry of Water Resources;
In order to ascertain the impacts of microorganism(bacillus subtilis)on soil improvement and water movement in saline alkali soil,a laboratory 1Dinfiltration experiment of brackish water with different concentrations(0g/L,1g/L,2g/L,3g/L and 4g/L)was conducted.The results showed that:(1)Bacillus subtilis reduced the infiltration capacity of the soil significantly,and slowed down the water flow.Compared with the control,the cumulative infiltration and the final wetting front distance were significantly decreased in soil with bacillus subtilis.The reduction in the cumulative infiltration was up to 40.97% under the brackish water concentration of 2g/L.The wetting front distance showed the similar results as infiltration.(2)Philip and Kostiakov infiltration model were used,and the fitting result showed that the imbibition rate Sof Philip formula was less than that in the corresponding control groups.This suggested the diminished solid water absorbing ability of capillary force might be due to the viscosity property improvement made by bacillus subtilis.The experience coefficient K of Kostiakov formula was smaller than the control,which indicated that the initial infiltration rate of bacillus subtilis contained solid was lower.Nevertheless,the empirical exponentialβwas greater than the control,demonstrating that the containing solid capacity of bacillus subtilis was fading with the increasing infiltration time.(3)After the infiltration of brackish water,the soil with bacillus subtilis showed a better aggregate structure,which could significantly improve the ventilationand water holding capacity.Soil water characteristic curve showed that,with the same moisture content and concentration,the water suction of the bacillus subtilis containing solid was stronger than the corresponding control,with more reduced matrix potential,which indicated that bacillus subtilis increase the water holding capacity and inhibit the water evaporation and infiltration.Finally,the soil water characteristic curve was fitted using van Genuchten model.In this formula,the soil residual water content,saturated water content and coefficient associated with intake value increased,and shape coefficient decreased.(4)In conclusion,bacillus subtilis can improve the solid structure effectively and reduce solid infiltration.This study could provide a theoretical support for the microorganism application in soil improvement.
【Fund】： 国家自然科学基金项目(51239009 41371239);; 陕西省科技支撑项目(2013KJXX-38);; 陕西省自然科学基金项目(2015JQ5161);; 西安理工大学特色研究计划项目(2016TS013)
【CateGory Index】： S156.4
【CateGory Index】： S156.4