Variation of Surface Soil Quality Parameters by Intensive Donkey-Drawn Tillage on Steep Slope

Abstract

Few direct measurements are made to quantify the erosion from upslope to lower field boundaries by intensive tillage. We conducted 50 plowing operations over a 5-d period using a donkey-drawn moldboard-plow on steep backslope in the Chinese Loess Plateau. Topographic changes at different slope positions were quantified using differential global positioning system (DGPS). Soil organic matter (SOM), extractable P and N, and soil bulk density were measured along a downslope transect after each 10-tillage series. Fifty operations resulted in a decrease in maximum soil surface level (SSL) of 1.25 m in the upper slope position and an increase of 1.33 m at the bottom of the slope. Slope gradients decreased from 37 to 14° at the upper position and from 18 to 0° at the lower position. Surface soil bulk density increased from 1.14 to 1.28 Mg m−3 in the upper slope and decreased from 1.10 to 1.03 Mg m−3 in the middle slope. Mean SOM concentrations in the upper and middle positions of the slope decreased from 8.3 to 3.6 g kg−1, mineral N from 43.4 to 17.4 mg kg−1, and Olsen-P from 4.5 to 1.0 mg kg−1 Intensive tillage resulted in a short-term increase in SOM and available nutrients in the lower portion during the tillage operations. Geomorphologic evolution and landscape variability of dissected hillslopes are attributable to soil movement and resulting physical and fertility degradation induced by intensive tillage.