Soil Aggregates and Primary Particles Transported in Rill and Interrill Flow
1980
Alberts, E. E. | Moldenhauer, W. C. | Foster, G. R.
The size distribution of soil particles detached and transported in rill and interrill flow was determined on a silt loam soil in northcentral Indiana. Eroded soil was separated by field and laboratory sieving into > 2-, 2- to 1-, 1- to 0.5-, 0.5- to 0.21-, 0.21- to 0.05-, and < 0.05-mm size classes. The amount of primary clay (< 0.002 mm) transported as discrete particles in rill and interrill flow was also determined. Large differences were found in the size of soil aggregates and primary particles in rill and interrill sediment. Rill flow transported a greater proportion of larger particles as compared with interrill flow because of basic differences in the detachment and transport mechanisms. Less than 5% of the rill and interrill sediment was composed of primary clays, indicating that most eroded clay was transported within soil aggregates. The primary particle composition of the eroded aggregates was also determined. For all sizes > 0.05 mm, the percentage of sand in rill and interrill sediment was considerably higher than that in the matrix soil. The high sand content decreased the percentage of silt in some size classes more than the percentage of clay, indicating that primary clays may either flocculate or adsorb to the surfaces of larger aggregates during transport. Water was added to the top of preformed rills at several rates to simulate various upland slope lengths. Discharge and rill erosion rates were not related for this soil that had not been tilled or cropped for 1 year.
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