Evaluating soil quality-soil redistribution relationship on terraces and steep hillslope

Soil redistribution from tillage and water erosion have the potential to modify the spatial patterns of soil quality on terraced and steep cultivated hillslopes. However, few studies have investigated this relationship. Our objectives were to quantify soil quality parameters along terraced and steep hillslopes and determine the relationship between soil redistribution from tillage erosion and water erosion on soil quality parameters in the Chinese Loess Plateau. Soil quality indicators, i.e., soil organic matter (OM), available P, N, bulk density (D-b), and clay and silt contents were measured at 5-m intervals on a terraced field and at 10-m intervals on a steep cultivated hillslope in a down slope transect. Soil redistribution rates from tillage and overland flow were obtained by Cs-137 technique integrated with a tillage erosion prediction model (TEP). Water erosion was the primary cause for the overall decline in soil quality on the steep cultivated hillslope while tillage erosion had a comparable contribution to overall level in soil quality on the terraced hillslope. Soil movement by tillage controlled the spatial patterns in OM, N, and P on both terraced and steep cultivated hillslopes. Selective removal of finer particles by water erosion caused a linear decrease in clay content of 0.02% m(-1) and corresponding increase in silt content of 0.04% m(-1) downslope on the steep cultivated hillslope. The impact of tillage erosion on OM, N, and P on the steep cultivated hillslope can be assessed using the change in adjacent slope gradients (X) through a soil quality-topography regression model, Y = aX + b.