Effect of exchangeable sodium percent on surface sealing
Abstract Laboratory studies were conducted to evaluate the effect of exchangeable sodium percent (ESP) on soil surface sealing and of surface sealing on infiltration and evaporation processes. Surface seals with hydraulic conductances 52.20 × 10 −3 , 49.20 × 10 −3 , 39.00 × 10 −3 , 33.00 × 10 −3 , and 17.91 × 10 −3 h −1 were attained on top of a sandy loam soil with ESP of 4 by placing a 5-mm layer of the same soil with ESP's 6, 10, 20, 30, and 60 respectively. Surface sealing increased with increasing ESP and appeared complete at ESP 30. Evaporation remained unaffected by the seals. Infiltration, however, was considerably reduced. Soil water profiles, which largely depended on the amount of infiltrated water, tended to become uniform. Equal moisture contents were also observed under evaporation.
Water Droplet Impact and its Effect on Infiltration
ABSTRACT THE effect of droplet impact on the infiltration characteristics of a Warden silt loam soil were investigated in the laboratory. The hydraulic resistance of the seal formed on the soil surface by impacting water droplets was found to increase with increasing droplet kinetic energy per unit soil surface area (KEa). Experimental data also showed that the depth of water infiltrated prior to surface ponding decreased with increasing application rate (rainfall intensity), kinetic energy per water droplet (KEd), and water droplet energy flux (DEf). A unique relationship between DEf and the depth infiltrated prior to ponding was noted for the Warden silt loam. A procedure for determining the depth of water that can be applied to the Warden silt loam without the potential for runoff based on this relationship and an equation for computing DEf was presented. It appears that DEt, which is a function of both application rate and KEd, may be more effective in evaluating the runoff potential of irrigation sprinklers and rainstorms than application rate alone on soils prone to surface sealing such as the Warden silt loam.
Strength of Compacted Amarillo Fine Sandy Loam as Influenced by Moisture, Clay Content, and Exchangeable Cation 1
UNCONFINED COMPRESSION STRENGTH OF AMARILLO FINE SANDY LOAM WAS AFFECTED BY WATER CONTENT /AT MOLDING AND AT TIME OF STRENGTH TEST/ BULK DENSITY, CLAY CONTENT, AND SATURATING CATION. WHEN DRIED AFTER MOLDING, BRIQUETTES OF AMARILLO FINE SANDY LOAM ATTAINED MAXIMUM STRENGTH AT 3 TO 6% WATER DEPENDING ON CLAY CONTENT. MAXIMUM STRENGTH WAS ATTAINED AT APPROXIMATELY ONE MONOLAYER OF WATER ON THE TOTAL SURFACE AREA SUGGESTING THAT H-BONDING OF WATER MOLECULES CONTRIBUTES TO SOIL STRENGTH. AS ADDITIONAL WATER WAS LOST, STRENGTH DECREASED TO A MINIMUM AT ONE-HALF MONOLAYER AND INCREASED AGAIN AS COMPLETE DRYNESS WAS APPROACHED. SHAPES OF THE DRYING CURVES WERE SIMILAR REGARDLESS OF THE PERCENT MOLDING WATER, BULK DENSITY, CLAY CONTENT, OR EXCHANGEABLE CATIONS. NA-SATURATED SOILS HAD GREATER DRY STRENGTH THAN CA- OR AL-SATURATED SOILS. /AUTHOR/