Spatial variability of hydraulic conductivity and sodium content of desert soils: implications for management of irrigation using treated wastewater.

摘要

Information on soil hydraulic properties, spatial variability, and relation to soil chemical properties is crucial for making management decisions for lands affected by anthropogenic activities. Proper management strategies based on the spatial variability of soil hydraulic properties are necessary to reduce the detrimental effect on soil environment due to the continuous application of wastewater. In situ infiltration tests were conducted at the West Mesa Land Application Facility near Las Cruces, New Mexico, to determine the spatial variability of hydraulic properties and quantify the macroporosity using tension infiltrometry. Infiltration tests were conducted for an hour at the center of 50x50 m sampling grid at pressure heads ( Psi ) of -30, -20, -10, -5, and 0 cm during March-April 2009. Wooding's equation was used to calculate saturated (K_s) and unsaturated (K( Psi )) hydraulic conductivity from the steady-state infiltration rate. Coefficients of variation (CV) for each of the five classes of K_s were low to moderate, and semivariograms displayed both short and long range variability. Kriged maps of K_s showed that classes I, II, and III were concentrated at the northeast and southwest sides of the study site, where higher Na+ was detected, and classes IV and V were at the center of the study site, corresponding to lower Na+ levels. Significantly lower macroporosity was observed in the area were Ks was lower and Na+ content higher. Therefore, additional increases in Na+ could further decrease the K_s and macroporosity and may affect water uptake by the native vegetation. Change in the wastewater application pattern by applying higher amounts of wastewater in the areas where soil Na+ concentrations are lower would be beneficial for sustaining soil quality and plant community.