Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/22/2009
Publication Date: 11/1/2010
Citation: Mudgal, A., Anderson, S.H., Baffaut, C., Kitchen, N.R., Sadler, E.J. 2010. Effects of long-term soil and crop management on soil hydraulic properties for claypan soils. Journal of Soil and Water Conservation Society. 65(6):393-403. Interpretive Summary: Regional and national soil maps available in the U.S. describe the spatial range of the main soil series. Associated databases give values for the properties of these soils, which are used by engineers, scientists, and soil and water resource managers when they need to know soil characteristics. However, these are approximate values and can vary within a soil due to management differences or other factors. This study was conducted to test whether soil hydraulic properties, which relate to the movement and storage of water, can be significantly affected by long-term soil and crop management. Soil samples were obtained from two fields with Mexico silt loam, a common soil in Northeast Missouri with very low permeability, a quality related to the ability for water to move through the soil, and a high runoff potential. One field has been under continuous row crop cultivation for over 100 years while the other one is a native prairie that has never been tilled. Four soil hydraulic properties were measured in the laboratory - soil water content, porosity, permeability, and bulk density. Permeability was also measured in both fields by an in-situ method that does not require sampling. Results showed significant differences in all hydraulic properties with the soil from the row crop field being significantly more compact, less permeable and holding less water than the prairie soil, indicating that row crop cultivation has significantly altered the hydraulic properties of this soil. Scientists can use this information to illustrate changes in plant growth, runoff, and pollutant transport due to long-term land management by inserting these different values in computer simulation models.
Technical Abstract: Regional and national soil maps have been developed along with associated soil property databases to assist users in making land management decisions based on soil characteristics. These soil properties include average values from soil characterization for each soil series. In reality, these properties might be variable due to substantially different management, even for similar soil series. This study was conducted to test the hypothesis that for claypan soils, hydraulic properties can be significantly affected by long-term soil and crop management. Sampling was conducted during the summer of 2008 from two fields with Mexico silt loam (Vertic Epiaqualfs). One field has been under continuous row crop cultivation for over 100 years (Field) while the other field is a native prairie that has never been tilled (Tucker Prairie; TP). Soil cores (76 x 76 mm [(3.0 x 3.0 in)]) from six replicate locations from each field were sampled to a 60 cm (24 in) depth at 10 cm (3.9 in) intervals. Samples were analyzed for bulk density, saturated hydraulic conductivity (Ksat), soil water retention, and pore size distributions. Values of coarse (60 to 1000 µm [(0.0024 to 0.039 in)] effective diam.) and fine mesoporosity (10 to 60 µm [(0.00039 to 0.0024 in)] effective diam.) for the Field site (0.044 and 0.053 m3 m-3 [(0.044 and 0.053 in3 in-3)]) were almost half those from the TP site values (0.081 and 0.086 m3 m-3 [(0.081 and 0.086 in3 in-3)]). The geometric mean value of Ksat was 57 times higher in the native prairie site (316 mm h-1 [(12.4 in h-1)]) than in the cropped field (5.55 mm h-1 [(0.219 in h-1)]) for the first 10 cm (3.9 in) interval. Differences in Ksat values were partly explained by the significant differences in pore size distributions. The bulk density of the surface layer at the TP site (0.81 g cm-3 [(55.6 lb ft 3)]) was two-thirds of value at the Field site (1.44 g cm-3 [(89.9 lb ft-3)]), and was significantly different throughout the soil profile except for the 20 to 30 cm (7.9 to 12 in) depth. These results show that row crop management has significantly altered the hydraulic properties for this soil. Simulation models can utilize these hydraulic properties to estimate and illustrate differences in hydrologic response for these long-term soil management treatments.