SIZE-DISTRIBUTION OF ERODED SEDIMENTS IN THE RUNOFF WATER AS AFFECTED BY RESIDUE MULCH, SURFACE ROUGHNESS, AND DISCHARGE RATE
Abstract
Knowing the amount and size-distribution of sediments transported in the runoff water is important for bota erosion studies and farm planning. The effect of type and amount of crop residues, mulch cover, surface roughness, and runoff rate on the size-distribution of eroded sediments, as evaluated by the 13 50 index, was investigated in a field study using simulated rainfall, in Eldorado do Sul-RS, Brazil, during the period of 1992 to 1994. The soil used in the experiment was a red-yellow podzolic, clay loam in texture, with 0.066 m/m slope. Treatments consisted of no-till, chisel plow, and plow-and- disk all of them in the presence and absence of cornstalk and wheat straw. The D50 index increased with runoff discharge up to a given size of eroded sediments and decreased thereafter, regardless of mulch cover and surface roughness. This was explained in terms of amount of sediments readily available for transport and in terms of available runoff energy to deteach new sediments. For a given runoff rate, the 13 55 index values decreased with mulch cover and surface roughness.
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