SOIL PROPERTIES ASSOCIATED WITH LANDSCAPE POSITION

Yield differences among landscape positions have been attributed to soil erosion and differences in plant-available water, soil texture, bulk density, and surface soil thickness. The objective of this study was to determine the extent to which soil chemical properties and soil texture varied among landscape positions. Soil samples were taken to a depth of 120 cm from the upper interfluve, lower interfluve, shoulder, upper linear, lower linear, and footslope positions at each of four sites located in eastern Nebraska. Significant differences among landscape positions were found for 13 soil properties. Sand, silt, pH, CaCO3, extractable Ca and Mg, exchangeable Ca, and base saturation generally increased downslope, while clay, organic matter, cation-exchange capacity, and available K generally decreased downslope. Highest concentrations of available K occurred on the upper interfluve, lower interfluve, and footslope; lowest concentrations were found on the upper and lower linear slopes. Management practices appear to have influenced pH, electrical conductivity, available P and K, and exchangeable K, particularly in the upper 30 cm. Drought conditions during the 1988 growing season resulted in carryover of NO3-N in the upper 30 cm. Nitrate-N in 1990 was leached to deeper depths.