Effect of Solute Type and Salinity on Soil Water Retention Curve

Soil water retention curve provides the important scientific basis for studying the movement and control of soil water. So far, most related researches and achievements have showed that soil properties have a certain impact on the soil water retention curve, but seldom has the academic circle attached importance to characteristics of liquid film. Therefore, the subject of study is black gunny soils in orchards in Zhengchuan Village of Qin'an County in Gansu Province. And we investigate the influence of NaCl and Na2SO4solutions of different salinity(0, 1, 3, 5 and 10 g L-1) on the soils water retention curve and the parameters of Van Genuchten equation using a centrifuge method. The results show that the salinity has a certain impact on the content of saturated water: the lower salinity( 3 g L-1) has impact on the soil water holding curve within low suctions(pF 2.5), but the higher salinity(≥ 3 g L-1) has impact on soil water holding curve within suctions(pF within 0 ~ 4.2). The content of soil moisture(θv) is the lowest by treated with the NaCl and Na2SO4solutions of salinity = 5 g L-1, and the treatments are significantly different with the control(salinity = 0 g L-1). The influence of salt type on variety velocity of parameters of Van Genuchten equation is different under equal salinity. Salt type has more obvious influence on the parameter α than the parameters θsand n, and the parameter n has a minimum influence. The parameters of variety velocity, i.e. a and n, are both significantly increased at the initial stage and then decreased with the increase of the salinity of NaCl, but the parameters of variety velocity, i.e. a and n, were both significantly decreased firstly and then increased with the increase of the salinity of Na2SO4. The NaCl solution has greater influence on soil water holding curve than Na2SO4.