Sediment-laden runoff from sloping upland vegetable fi elds during heavy storms in Korea hasnegatively affected on the quality of rivers and man-made lakes that are important to domesticwater supply. A common characteristic of the fi elds is that the soil surfaces are not generallycovered either crop residues or crop canopy during monsoon season because vegetable doesnot leave stable residues. Soil erosion is affected by rainfall amount, intensity and duration,soil texture, crop, tillage, surface cover, slope and slope length, runoff and velocity, besidesthe other agricultural practices. Once muddy runoff occurred, it is very diffi cult to control ormanage it. Therefore, the fi rst and the best measures are to reduce soil erosion and runoffat sources. The objectives of this research were to experimentally investigate the effect ofsurface mulch composed of rice straw mat, PAM and gypsum on the reduction of runoff andNPS pollution loads under natural rainfall conditions. The test was conducted on a Chinesecabbage fi eld.
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