Effects of long-term soil and crop management on soil hydraulic properties for claypan soils

Abstract

Various land management decisions are based on local soil properties. 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). Soil cores (76 × 76 mm [3.0 × 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 (K_sat), soil water retention, and pore-size distributions. Values of coarse (60 to 1,000 μm [0.0024 to 0.039 in] effective diameter) and fine mesoporosity (10 to 60 μm [0.00039 to 0.0024 in] effective diameter) for the Field site (0.044 and 0.053 m³ m⁻³ [0.044 and 0.053 in³ in⁻³]) were almost half those values from the Tucker Prairie site (0.081 and 0.086 m³ m⁻³ [0.081 and 0.086 in³ in⁻³]). The geometric mean value of K_sat was 57 times higher in the native prairie site (316 mm h⁻¹ [12.4 in hr⁻¹]) than in the cropped field (5.55 mm h⁻¹ [0.219 in hr⁻¹]) for the first 10 cm (3.9 in) interval. Differences in K_sat values were partly explained by the significant differences in pore-size distributions. The bulk density of the surface layer at the Tucker Prairie site (0.81 g cm⁻³ [50.6 lb ft⁻³]) was two-thirds of the 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 and its effect on soil loss have significantly altered the hydraulic properties for this soil. Results from this study increase our understanding of the effects of long-term soil management on soil hydraulic properties.