Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 27, 2007
Publication Date: May 1, 2008
Citation: Feyereisen, G.W., Strickland, T.C., Bosch, D.D., Truman, C.C., Sheridan, J.M., Potter, T.L. 2008. Curve Number Estimates for Conventional and Conservation Tillages in the Southeast Coastal Plain. Journal of Soil and Water Conservation Society. 63(3):120-128. Interpretive Summary: Hydrologic models are used to estimate the effects of agricultural practices on stream water quality and quantity. The information input to the models often comes from standard tables which provide values for average conditions of landuse and soil type. Generally, better results can be obtained when input values are derived from experiments conducted on the soil types and land uses that are being modeled. Rainfall-runoff data from 1999-2005 measured at a field study site near Tifton, Georgia have been used to calculate curve numbers for conventional and conservation strip tillage for a cotton-peanut rotation on a Tifton loamy sand. The results showed that strip tillage reduced runoff compared to conventional tillage. There was a greater difference between the two tillage types during the growing season. Under wet soil conditions during the dormant season, there was no difference in runoff propensity between the two tillages. The results indicate that hydrologic models that reflect the difference in seasonal curve numbers for strip tillage would better be able to predict runoff and consequently water quality effects.
Technical Abstract: Rainfall-runoff data measured from 1999-2005 at a field study site in south Georgia were used to calculate curve numbers by averaging, log-normal, and data-censoring methods. For average antecedent moisture conditions, curve numbers by the average method for conventional and strip tillages were 89 and 84, respectively, and by the log-normal method were 89 and 83, respectively. Results from the data-censoring method were 75 and 81, respectively, which matched standard table values developed from a long-term series of annual maximum runoff. Curve numbers for strip tillage were 83 and 88 for growing and dormant seasons, respectively; however, there was no difference between growing and dormant season, 89, for conventional tillage. Under wetter than normal soil conditions during the dormant season, the curve number for both conventional and strip tillage was 95. The results indicate that hydrologic modeling of Coastal Plain watersheds would be improved if curve number were varied seasonally.