| heal.abstract |
Tillage erosion is considered one of the most important processes of land degradation in hilly cultivated areas. Extensive cultivation of hilly areas have largely degraded soil in the past decades due to the erosion caused by use of heavy powerful tillage implements. In order to evaluate the eject of moldboard plow on tillage erosion, a study was conducted along an intensively cultivated hillslope (slope gradient from 6-22%) with rainfed crops. Two tillage experiments were carried out, one with the tillage implement moving perpendicular and the other parallel to the contour lines. The soil displacement by tillage was measured by using tracers (numbered aluminum cylinders of 1 cm3 volume) that were inserted into the soil at various depths at selected slope positions to give a range of slope gradients. Thirty strips were prepared and 1200 tracers were inserted into the soil for each experiment. The location of each tracer was precisely recorded using a theodolite before and after the tillage operation. Soil displacement was analyzed for three plow depths (20 cm, 30 cm, and 40 cm) and for two directions of tillage operation in each experiment. The effect of long term moldboard plowing on tillage erosion in the study hillslope was examined by using past and present detailed soil survey data, existing water erosion data, and empirical relationship data derived from this study. Downslope displacement of soil during tillage increased with increased plow depth and slope gradient. In steep hillslope positions (22% slope gradient), a maximum soil displacement of 97 cm was measured after plowing the soil downslope at the depth of 40 cm and perpendicular to the contour lines. After plowing the soil along contour lines, under the same soil conditions, and management practices, soil displacement was reduced to 69 cm. A 50% reduction in plow depth reduced soil displacement by more than 75%. The upslope reversion of furrow with the tractor moving parallel or perpendicular to the contour lines significantly reduced soil displacement, from 2-33 cm. The comparison of two tillage experiments showed that contour farming significantly decreased tillage erosion. The analysis of detailed soil survey data, water erosion data, and tillage erosion data demonstrated that tillage erosion was the most important process transporting soil from the upper convex to the lower concave parts of the study hillslope. |
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