Sediment Yield from a Mississippi Delta Cotton Field1
- F. E. Dendy2
Sediment yield from flat (0.2% slope) delta fields was measured during a 33-month study. Annual erosion rates were higher than anticipated, ranging from a maximum 12 metric tons ha−1 for a year of above normal rainfall to a minimum 5 metric tons ha−1 for a year of slightly below normal rainfall. Highest sediment concentrations in runoff occurred in the spring during the seedbed preparation and planting season when the soil was bare of vegetative cover, freshly plowed, and highly susceptible to erosion. Lowest concentrations occurred in September and October when vegetative cover was good.
Sediment particle size data from selected storms showed that about 83% of the sediment removed from the fields was < 2 µm in diameter and nearly all, 98% was < 16 µm. Field soils were composed of 24% clay, 23% silt, and 53% sand, so considerable enrichment of fine particles occurred during the erosion process. This indicates that most sediment deposits in streams and lakes of the area are composed of fine materials and that gradual enrichment of coarse particles in the soils is occurring over long periods of time.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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