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United States Department of Agriculture

Agricultural Research Service

Title: Soil Hydraulic Properties of Cropland Compared with Reestablished and Native Grassland

Authors
item Schwartz, Robert
item Evett, Steven
item Unger, Paul - USDA-ARS RETIRED

Submitted to: Geoderma
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 2, 2002
Publication Date: N/A

Interpretive Summary: Conversion of cropland to perennial grasses will, over time, produce changes in soil hydraulic properties. We conducted a study to characterize and compare soil hydraulic properties on adjacent native grassland, recently tilled cropland, and reestablished grassland in the Conservation Reserve Program (CRP) at three locations in the Southern Great Plains. Soil cores were sampled to determine water retention properties. Hydraulic conductivity was determined using a tension infiltrometer. Soils in CRP had greater surface bulk densities and lower infiltration rates than their grassland and cropland counterparts. Land use practices had a greater effect on water movement than did soil series indicating that the modifying effects of tillage, reconsolidation and pore structure evolution are important processes governing infiltration in fine-textured soils.

Technical Abstract: Conversion of cropland to perennial grasses will, over time, produce changes in soil hydraulic properties. We conducted a study to characterize and compare soil hydraulic properties on adjacent native grassland, recently tilled cropland, and reestablished grassland in the Conservation Reserve Program (CRP) at three locations in the Southern Great Plains. A tension infiltrometer was used to measure unsaturated infiltration over a range of water potentials at the soil surface. Intact soil cores were sampled within the Ap and Bt horizons to determine bulk density and water desorption curves. Unsaturated hydraulic conductivity over the range in pressure heads was estimated using Wooding's equation for steady state flow from a disc source. Soils in CRP had greater surface bulk densities than their grassland and cropland counterparts. The shape of the soil water retention curve for grassland and CRP land were similar suggesting that converted croplands had fully reconsolidated. Mean near-saturated hydraulic conductivities of cropland were not significantly different from grassland. However, at -1.5 kPa supply pressure, cropped soils had a mean unsaturated conductivity 1.4 and 4 times greater than CRP land and grassland, respectively. Sites in CRP had the lowest (P < 0.05) near-saturated hydraulic conductivities, which suggests that, after 10 years, grasses had not fully ameliorated changes in pore structure caused by tillage. Land use practices had a greater effect on water movement than did soil series indicating that the modifying effects of tillage, reconsolidation, and pore structure evolution on hydraulic properties are important processes governing water movement in these fine-textured soils.

Last Modified: 7/30/2014
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