Study on Hydraulic Parameters of Irrigating Warped Soil in Ningxia Irrigation Area

A systematic research on hydraulic parameters of irrigating warped soil in Ningxia irrigation area is shown in this article.The results indicated as: the variation of saturated hydraulic conductivity of undisturbed soil and disturbed soil is 10~100 cm/d and 3~50 cm/d respectively.The dynamics of saturated hydraulic conductivity along the soil profile of the undisturbed soil is consisting with that of the disturbed soil: the saturated hydraulic conductivity presents reciprocating change with the increase of depth.The saturated hydraulic conductivity of undisturbed soil and disturbed soil are affected by clay content,bulk density,and porosity,except organic matter content.The saturated hydraulic conductivity of undisturbed soil is bigger than disturbed soil,with the general ratio of 2~5 times,and the variability is bigger too.Tendencies of soil water retention curves of all soil layers are similar,the soil volumetric water content decreased with the increase of soil water suctions,and it will stable when the suction reach a certain value,the soil water retention curve is affected by the clay content dramatically.The soil moisture diffusivity of all soil layers is changeable from 1.0×10-3~6 cm2/min,and the soil moisture diffusivity of upper soils are far smaller than the lower's.Relationship between soil moisture diffusivities and soil volumetric water content in every soil layer are sharply positive exponential function,which was fitted by the empirical equation: D(θ)=aebθ.The soil moisture diffusivity is affected by soil clay content,porosity,soil bulk density,and organic matter content.