Wind Erodibility of Organic Soils

Intensively cropped organic soils are often subject to severe wind erosion. The objective of this study was to measure their physical wind erodibility properties. Four organic soils were collected from Florida, North Carolina, and Michigan. The organic matter content, aggregate density, dry-aggregate stability, aggregate size distribution, and soil water characteristics were measured. Trays (122 by 20 by 6 cm) were filled with field-sampled soils and sieved soils with 80% of aggregates <0.84 mm. Trays of both crusted and uncrusted soil were place in a laboratory wind tunnel and exposed to wind of various speeds. Aggregate densities ranged from 0.93 to 1.13 Mg m -3 , which is less than typical mineral soils. Dry-aggregate stability was relatively high [2.9-4.7 In(J kg -1 )]. Threshold friction velocity varied from 0.40 to 0.83 m s -1 for the field condition and from 0.27 to 0.31 m s -1 for the soil with 80% of the aggregates <0.84 mm. The aggregate abrasion coefficients ranged from 0.0006 to 0.0136 m -1 , meaning the aggregates should be moderately resistant to abrasion losses. The crust abrasion coefficients varied from 0.039 to 0.123 m -1 . Hence, a crusted soil surface should abrade more easily than a well-aggregated soil. The loose erodible material on the crusts ranged from 0.010 to 0.068 kg m -2 and varied directly with sand content and inversely with organic matter. The threshold friction velocities of organic soils were slightly higher than would be predicted for comparable mineral soils. From the results of this study, it is expected that for a given wind speed, a nearly equal mass of soil would be eroded from organic soils as from comparable mineral soil.