Carbon Transported via Sediments

Although differences and trends in sediment transport can be noted based on tillage practice or crop year (Table 18.3), the year-to-year variation was so great that there were not significant differences among the values reported. The standard deviation was almost always greater than the mean for each practice and year. This was also true for the transport of C in the sediments. The lowest annual sediment transport occurred with no till and the highest with disk. With the exception of the chisel-plow practice, average annual total sediment losses (combined wheel and flume floor sediment) were 2.8 to 8.5 times greater with soybeans than corn. Total sediment C transport had similar ratios (2.7 to 7.7 times) (Owens et al., 2002a).

Large events in June 1990 resulted in a monthly average sediment transport and carbon transport much greater than any other month. In spite of the large monthly differences, there were no significant differences among monthly averages because of the great variability in event sizes and occurrences. A few large events usually transport most of the sediment (Edwards and Owens, 1991). The monthly distribution of C transport closely followed the pattern of sediment transport because the monthly C concentrations did not vary greatly.

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