Saturday, 15 July 2006

Wind Erosion Effects on Soil Properties: A Case Study at Big Spring, Texas.

R. Scott Van Pelt and Ted M. Zobeck. USDA-ARS, Cropping Systems Research Laboratory, 302 West I-20, Big Spring, TX 79720

Wind erosion degrades soils by several processes including winnowing of fine chemically active soil fractions and, in extreme cases, removal of the entire epipedon. A 91 m radius circle in a 7.5 ha field of Amarillo fine sandy loam (fine mixed thermic Paleustalf) was kept in a bare erodible condition during the fallow season for 12 years in order to take detailed measurements of wind erosion during high velocity wind events. A 6m wide strip along the circumference of this circle was designated as the deposition area and tilled with raised beds in order to capture saltating sand emanating from the circle. The remainder of the field was kept in non-erodible condition. From measurements taken in the field, more than 10 cm of soil loss occurred in the eroded area and more than 30 cm of sand was deposited in the deposition area. Data collected from three crops grown on the field during the 19972003 growing seasons indicated that the best growth was obtained in the deposition area and the poorest growth was obtained in the eroded circle. We sampled the soils in the non-eroded, eroded, and depositional areas in order to determine what soil factors may be responsible for the growth responses. We found that the much of the original Ap horizon had been removed from the eroded area resulting in exposure and tillage mixing of the upper Bt horizon and an increase of clay content with respect to the non-eroded sites. The deposition area became increasingly sandy during this time period, but the fine sand fraction was lower than the non-eroded sites indicating that medium sand was the primary aeolian material deposited. Soil nutrient analysis indicated that nitrate was significantly lower and manganese was significantly higher in the eroded area, but no other significant nutrient differences were noted. Infiltration depth data obtained with mini-lysimeters indicated significant differences among all three areas with the greatest depth of infiltration observed in the depositional area and the least depth in the eroded area. Evaporation rate data obtained with the mini-lysimeters indicated significantly less evaporation in the depositional area compared to the other two areas. Penetration resistance data indicated that the depositional area has the least resistance to penetration and the non-eroded area had the greatest resistance. From this case study, we conclude that wind erosion degraded many physical and chemical characteristics of the soil in the eroded area and enhanced the physical soil characteristics in the depositional area. We believe the growth responses noted were the result of a number of soil-related factors differing among the areas including nutrient availability, precipitation capture efficiency, and resistance to root penetration.

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