枯草芽孢杆菌对盐碱土水分运动和水稳性团聚体的影响

为探明微生物在盐碱地改良方面的应用,通过在盐碱土中加入枯草芽孢杆菌,研究不同浓度微咸水(0,1,2,3,4g/L)条件下,盐碱土中的水分运动和土壤水稳性团聚体的变化规律。结果表明:(1)枯草芽孢杆菌可以显著减少土壤的入渗能力,同时可减缓水分的迁移能力,添加枯草芽孢杆菌的土壤与相对应的对照组相比,累积入渗量和湿润锋推进距离均显著减少,其中在微咸水浓度为2g/L时,土壤累积入渗量减少幅度最大,为40.97%,其他处理减少程度依次为3,0,1,4g/L,湿润锋的推进距离也有类似的结果。(2)利用Philip和Kostiakov入渗模型拟合试验数据,发现Philip公式中的吸渗率S均小于相相应对照组,Kostiakov公式中的经验系数K均小于相应对照组,而经验指数β均大于相应对照组。(3)枯草芽孢杆菌可以增加土壤的保水能力,在微咸水浓度为2g/L时,对土壤水吸力的影响较大。与对照组相比,van Genuchten公式中土壤滞留含水率θr、饱和含水率θs及与进气值相关系数α均有所增大,形状系数n逐渐减小。(4)含有枯草芽孢杆菌的土壤,在微咸水入渗后其土壤团粒结构均有较大的改善。

Effects of Bacillus Subtilis on Water Movement and Water Stable Aggregate in Saline Alkali Soil

In order to ascertain the impacts of microorganism (bacillus subtilis) on soil improvement and water movement in saline alkali soil,a laboratory 1D infiltration experiment of brackish water with different concentrations (0 g/L,1 g/L,2 g/L,3 g/L and 4 g/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 2 g/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 S of 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 exponential β was 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 ventilation and 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.