Submitted to: Management of Landscapes Disturbed by Channel Incision Stabilization Rehabi
Publication Type: Proceedings
Publication Acceptance Date: March 7, 1997
Publication Date: N/A
Interpretive Summary: This paper was written for presentation at a conference attended by many non-erosion scientists. Research results from standard erosion plots and small unit watersheds at Holly Springs were used to show the benefits of conservation tillage for reducing sediment yield. Gross erosion was defined as the sum of soil erosion within unit areas throughout a watershed, while sediment yield, in contrast, was explained to be the amount of sediment leaving a watershed. Measured plot erosion was used to estimate some of the factors in the Revised Universal Soil Loss Equation (RUSLE), which then was used to estimate gross erosion on three watersheds for different cropping practices in different years. Gross erosion computations for conventional-till crops illustrated the erosion potential of moderately to steeply sloping watersheds in northern Mississippi. Comparisons of these high rates to those computed for conservation tillage illustrated the effectiveness of conservation tillage treatments in reducing gross erosion. Measured sediment rates at watershed outlets also showed that low sediment yields can be obtained with conservation tillage. Differences between gross erosion and sediment yields during different study periods indicated the variability that can occur between gross erosion and sediment yield rates from watersheds. Terraces were effective in reducing gross erosion, and a grass waterway was effective in trapping sediment delivered to the waterway. No-till practices were more effective than terraces in reducing erosion; however, research is needed to improve RUSLE routines for estimating P-factor credit for contoured rows of no- till crops. These results will be useful to farmers and to extension and conservation action agencies.
Technical Abstract: Conservation tillage reduced upland erosion and sediment yield from research watersheds. Measured plot erosion was used to estimate some of the factors in the Revised Universal Soil Loss Equation (RUSLE), which then was used to estimate gross erosion on three watersheds for different cropping practices in different years. Estimates of gross erosion for soybean and wheat grown in contoured, no-till rows during 1970-1972 were 3.3 t/ha on one watershed and 2.1 t/ha on another. Measured sediment yields were 6.5 and 3.6 t/ha, respectively. On another watershed, estimated gross erosion for no-till corn for grain during 1975-1976 was 1.2 t/ha; the measured sediment yield was 0.5 t/ha. These values were much lower than the gross erosion of 51.5 and 28.6 t/ha estimated for conventional-till corn grown in up-and-downhill rows and contoured rows, respectively. A terraced watershed with conventional-till corn during 1964-1968 had an average sediment yield of 13.4 t/ha, which was one-half the 3-year average sediment yield before terraces were installed.