An Analytical Method for Relationship Between Hydraulic Diffusivity and Soil Sorptivity

A simple method was developed to relate soil sorptivity to hydraulic diffusivity and water absorption experiments were conducted utilizing one-dimensional horizontal soil columns to validate the relationship. In addition, an estimation method for hydraulic diffusivity with disc infiltrometer was developed. The results indicated a favorable fit of the theoretical relation to the experimental data. Also, the experiment with disc infiltrometer for estimating the diffusivity showed that the new method was feasible.

Optimal disc tension infiltrometer estimation techniques for hydraulic properties of soil under different land uses

Different land use,and associated variations in agricultural or silvicultural practices,can cause substantial variations in soils’hydraulic properties.Thus,the optimal method for measuring these properties may vary,even among neighboring sites.In this study these variations were examined by comparing measurements of hydraulic properties of soil in fields used for poplar,alfalfa and wheat cultivation obtained with two steady flow methods(the White and Sully,and single disc with multiple tension methods)and two transient flow methods(the single disc with single tension,and multiple tensions with multiple disc radius methods).The fields were all located in Changwu municipality,a major grain-producing area in Shaanxi Province,China.Disc tension infiltrometers were used to measure unconfined,unsaturated infiltration over a range of supply pressure heads(h=−9 cm,−6 cm,−3 cm and 0)at the soil surface.Intact soil cores were sampled near the surface to determine bulk density and soil water retention curves at potentials ranging from−0.15 kPa to−100 kPa.Unsaturated hydraulic conductivity values over the range of supply pressure heads were estimated using Wooding’s equation for steady-state flow from a disc source.The van Genuchten water retention model was fitted to experimental data to estimate the parameter values.The results indicated that land use affects soils’saturated and unsaturated hydraulic conductivity.Further,steady state flow methods are most appropriate for measuring hydraulic properties of soils under poplar and wheat,due to their high organic contents and saturated hydraulic conductivity.However,for soils supporting alfalfa(which are more homogeneous),instant methods provide better results,in addition to substantial time and labor savings.

Variation in soil infiltration properties under different land use/cover in the black soil region of Northeast China

Soil infiltration properties(SIPs)of infiltration rate and saturated hydraulic conductivity significantly affect hydrological and erosion processes,thus,knowledge of SIPs under different land use/cover are vital for land use management to control soil erosion for realizing the sustainable development of the small agricultural watershed.Nevertheless,few studies have been carried out to investigate the differences in SIPs and their dominant influencing factors between different land use/cover in the black soil region of Northeast China.Therefore,eight typical land use/cover were selected to clarify the variations in SIPs between different land use/cover and further identify their dominant influencing factors.SIPs of initial infiltration rate(IIR),steady infiltration rate(SIR),and saturated hydraulic conductivity(Ks)were determined under eight typical land use/cover(forestland,shrub land,grassland,longitudinal shelterbelt,transverse shelterbelt,agricultural road,and cropland of Zea mays L.and Glycine max(Linn.)Merr)using a tension disc infiltrometer with three pressure heads of−3,−1.5,and 0 cm.The results of one-way ANOVA analysis showed that SIPs varied greatly between different land use/cover.Shelterbelt plant with Populus L.had the maximum IIR,SIR,and Ks,and then followed by shrub land,agricultural road,cropland,grassland,and forestland.Spearman correlation analysis indicated that SIPs were significantly correlated with soil and vegetation properties.Redundancy analysis revealed that differences in SIPs between different land use/cover were dominantly attributed to the differences in soil texture,field capacity,and plant root mass density,which explained 79.36%of the total variation in SIPs.Among these dominant influencing factors,the results of structural equation model indicated that the indirect effects of plant root and soil texture played the most important role in variations of SIPs via affecting soil texture and pore characteristics.These results have significant implications for the precise prediction of watershed hydrological and erosion processes,also provide a scientific basis for guiding the distribution pattern of land use in the cultivated watershed.