Desert soils mostly from the Mojave Desert were tested for threshold friction velocity (the friction velocity above which soil erosion takes place) with an open‐bottomed portable wind tunnel. Several geomorphological settings were chosen to be representative of much of the surface of the Mojave Desert, for example, playas, alluvial fans, and aeolian features. Variables which increase threshold velocity are decreasing proportion of sand, increasing size of dry aggregates of the soil, and increasing fraction of the soil mass larger than 1 mm. Threshold velocity increases with different types of soil surfaces in the following order: distrubed soils (except disturbed heavy clay soils), sand dunes, alluvial and aeolian sand deposits, disturbed playa soils, skirts of playas, playa centers, and desert pavements (alluvial deposits).

Desert soils having clay crusts, mostly from the Mojave Desert, were tested for threshold friction velocity (the friction velocity at which soil erosion begins) with an open-bottomed wind tunnel. The soils were also tested for content of clay, water-soluble material, calcium carbonate, organic material, mineralogy of clay and of salts, soil moisture, modulus of rupture, and crust thickness. If no loose material existed on the soil surface, crusts having modulus of rupture greater than 0.7 bar and crust thickness of 0.7 cm to 0.3 cm were effective in protecting against wind erosion. Disturbed clay crusts having modulus of rupture before disturbance greater than 2 bar with thickness less than 1.9 cm did not experience significant wind erosion. Modulus of rupture was related to composition of soil but was shown to depend mostly on clay content. Soil composition is related to modulus of rupture in an empirical equation.

A 3‐year study was conducted on Austin clay at Temple, Texas, to determine the effect of mulches of straw, gravel, and soil treated with dioctadecyl dimethyl ammonium chloride (DDAC) on runoff, erosion, and evaporation. Mulches were applied to 0.01‐acre plots on a 4% slope. Plots were fallowed 2 years and planted in grain sorghum (Sorghum vulgare) the third year. Runoff and erosion were greater from DDAC‐treated soil than from bare‐check soil. A surface cover of straw or gravel reduced runoff significantly and essentially eliminated erosion. Both the 2‐inch straw mulch and the bare DDAC‐treated soil reduced evaporation significantly from the 0‐ to 6‐inch depth during a hot, rainless 10‐day period. Straw, gravel, and DDAC‐treated soil mulches were about equally effective in evaporation control over periods of a month or more. During high rainfall periods, straw and gravel mulches increased infiltration and movement of excess water below 54 inches. The effect of chemical treatments on runoff and erosion should be considered in addition to their ability to reduce evaporation of soil moisture.

Ground cover determined by light interception is the percentage of the soil surface shaded by the plant canopy; i.e., it is a measure of the shadow projected by the plant canopy. The best time to measure ground cover is near solar noon when changes in solar angle result in the least change in ground cover. Measurements of ground covered by canopy foliage are used to evaluate the effectiveness of sunlight interception in photosynthesis and evapotranspiration studies. Ground cover measurements are also useful indicators of the ability of various row crops and cropping systems to intercept rainfall and reduce runoff and erosion.Ground cover of grain sorghum [Sorghum bicolor (L.) Moench], cotton [Gossipium hirsutum L.], sunflower [Helianthus annus (L.)], soybean [Glycine max (L.) Merr.], and corn [Zea mays (L.)] were determined using a meter stick, overhead photography, and photosensitive light sensors.The meter‐stick method is as accurate, faster, simpler, and more economical than any of the other methods used to determine ground cover. There were no significant differences in ground cover determinations using the meter‐stick method, overhead photographs, spatial quantum sensor, or traversing quantum cell. Ground cover was not linearly related to Leaf area index (LAI). A single measurement of ground cover across the plant row (perpendicular) was as accurate as the average of 21 inter‐row measurements parallel to the plant rows.

Weighing lysimetry was used to determine evaporative fluxes from a natural shrinkage crack and from an artificially induced soil shrinkage crack. Evaporation from the soil surface, except at the crack opening, was prevented by covering the lysimeter with plastic film. Evaporation rates from the natural and induced crack averaged about 0.6 mm/day computed on the basis of the surface area of the lysimeter. The horizontal soil water flux in the liquid phase to the crack wall was quite low, indicating that most of the measured evaporation resulted from vapor transport from some distance in the soil pores to the crack walls. Diurnal variations in evaporation rates were closely related to diurnal changes in vapor pressure deficit of the atmosphere above the soil surface. Evaporation rates from the natural/crack experiment were practically the same when the crack and soil surface were exposed to the atmosphere as when only the crack opening was exposed. Therefore, most evaporation from cracked, dry clay soil occurs because of the presence of shrinkage cracks. The results suggest a possibility for conserving water by partially filling the shrinkage cracks with dry soil or mulch to reduce evaporation. The low evaporation rates measured, however, make the feasibility of such a practice doubtful.