Erosion and productivity of vegetable systems on sloping volcanic ash-derived Philippine soils
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Soil erosion is a significant threat to agricultural productivity on sloped lands. This paper assesses the effectiveness of several different soil conservation practices for vegetable systems on sloped volcanic ash-derived soils. A field experiment was conducted to test the authors' hypothesis that contouring, strip cropping, and high-value contour hedgerows (asparagus, pineapple, pigeonpea, and lemongrass) would reduce soil loss relative to the traditional up-and-down farming method. They found that up-and-down cultivation had the greatest annual soil loss, followed by high-value contour hedgerows, strip cropping, and contouring. For all test plots there was a large gradient in the soil characteristics and productivity between the upper and lower bounds of the plots; crop yields in the downslope sections were significantly higher. The contour hedgerow method caused rapid formation of bioterraces, which also showed much greater productivity in the bottom portions.