Tracing Moisture Movement in Slick Spot Soils with Radiosulfur: Part II

Abstract

AbstractA study was made of the pattern of moisture movement in slick spot and associated soils. Field experiments to trace moisture movement in slick spot soils were run on rangeland south of Boise and on irrigated land on the Black Canyon tract near Caldwell. Radiosulfur in the form of dilute sulphuric acid was absorbed by a wad of cotton. Each wad was specifically placed at a different depth in or adjacent to a slick spot. After several months, soil and plant samples from the areas indicated that characteristic patterns of moisture movement had occurred.On the tagged slick spots in the rangeland, the greatest concentration of activity, hence the least moisture movement, was in the B2t and B3sa horizons, the zones of maximum clay and salt accumulation, respectively. When the S35 was placed in the Cca horizon, the activity moved upward into the B3sa and B2t horizons, indicating the upward movement of moisture.When the tracer was placed in the Ap, top of the B2, or in the B3 horizon at the edge of the slick spot in the irrigated soils, there was movement downward and concentration in the C horizon. There was more concentration of activity in the direction toward the slick spot than away. Plants growing in the direction of the slick spot contained more radiosulfur than those growing in the direction away from the spot.The pattern of moisture movement in the associated soils, both in the rangeland and irrigated soils, was in all directions from the placements and had a low index value, indicating free movement of moisture throughout the profile.