Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/6/2005
Publication Date: 5/6/2005
Citation: Tekeste, M.Z., Raper, R.L., Schwab, E.B. 2005. Soil variability of soil cone penetration resistance as influenced by soil moisture on pacolet sandy loam soil in the southeastern united states. In: Proceedings of the 27th Annual Southern Conservation Tillage for Sustainable Agriculture, June 27-29, 2005, Florence, South Carolina. Interpretive Summary: Mapping the magnitude and depth of root restricting layers in Southeastern US soils would assist in soil compaction management by reducing the amount of energy required for tillage. This study was conducted to determine the influence of soil moisture on the magnitude and depth of the compacted layer on this sandy loam soil. The depth of the compacted layer was found to vary greatly across the field. Soil drying also appeared to decrease the predicted depth. Maps created from these measurements could be used to prescribe tillage depth and hence reduce the cost of production.
Technical Abstract: Soil hardpans found in many of the Southeastern USA soils reduce crop yields by restricting the root growth. Site-specific soil compaction management to alleviate this problem requires determination of the spatial variability and mapping of soil hardpans. The objective of this study was to determine the spatial variability of soil hardpan as influenced by soil moisture. Geo-referenced soil cone index measurements were taken in 200 grid cells (10 X 10 m2 grid cell size) on Pacolet sandy loam soil (Fine, kaolinitic, thermic Typic Kanhapludults) in Auburn, AL (USA) on June 25, 2004 and August 29, 2004 representing wet and dry soil measurement dates. Core samples were also taken in 5.08 cm depth increments up to a depth of 66.04cm for soil moisture and bulk density determinations. Statistical and geostatistical methods were used for the data analysis. In the 0-30 cm depth, the soil moisture had dried significantly by August 29, 2004 (Dry) as compared to the soil moisture on June 25, 2004 (Wet; P < 0.0001). An isotropic spherical semivariogram model best fit the semivariances of the peak cone index for wet (R 2 = 0.98) and dry (R 2 = 0.97) soil conditions. Soil drying increased the peak cone index and the maximum semivariance value (sill). Small but statistically significant differences (P < 0.0001) were also observed on the predicted depth to the peak cone index as the soil dried in the 0-30 cm depth. In the dry soil condition, the semivariances of the predicted depth to the peak cone index were nearly constant over the separation distances suggesting that the depth to the hardpan did not exhibit spatial dependence.