Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/24/2003
Publication Date: 4/30/2004
Citation: Wilson, G.V., Dabney, S.M., Mcgregor, K.C., Barkdoll, B.D. 2004. Tillage and residue management effects on runoff and erosion dynamics. Transactions of the ASAE. 47(1): 119-128. Interpretive Summary: Surface residue and tillage can significantly impact total runoff and soil losses. However, the impact on the timing and rate of runoff and the change in sediment concentrations in the runoff during storm events is not clear nor is the degree that the impacts of these management factors are carried over to the following year. This is particularly true when long-term conventional tillage (CT) systems are converted to no-till (NT) and long-term NT systems are converted to CT. The objective of this study was to determine the effects of tillage practices and residue management on the characteristics of the runoff and erosion patterns during events. Six-row wide plots that had been under CT or NT corn for 9 years were used in this study. Plots had an average slope of 5.7% on a Grenada Silt Loam soil. Rainfall was applied to each plot at a rate of 65 mm/h for one hour under naturally dry run conditions, followed by a second rain for 30 minutes four hours later under wet conditions, and finaly a third rain for 30 minutes just 30 minutes later under very wet conditions. The treatments consisted of combinations of CT and NT that were tilled and not tilled and that had residue left on the surface, removed from the surface just prior to rainfall, and removed from surface 1 year before and again immediately before the rainfall. Dye was released into the runoff at the top of the plots during the time of peak runoff to determine how fast flow was occurring over the surface. The time of runoff initiation, maximum runoff rates, velocity of runoff, and maximum sediment concentration were used to describe differences in runoff and erosion processes. Residue removal resulted in significantly sooner runoff with the NT system and this affect was carried over to the subsequent year. Maximum sediment concentrations were lower for the CT land that is not tilled than the tilled CT land despite the not tilled land having runoff sooner and at higher runoff rates. Tilling land that had been in NT resulted in significantly lower sediment concentrations than tilling land that had been in CT suggesting that the improvements in the NT soil were not immediately lost when it was tilled, but these beneficial properties were fully lost within one year of residue removal.
Technical Abstract: The carry-over affects from one year to the next of surface residue and tillage management decisions on runoff and erosion are not clear. This is particularly true when long-term CT systems are converted to NT systems or long-term NT converted to CT. The dynamics of runoff and erosion processes during rainfall events are likely dependent upon the tillage and residue management system. The objective of this study was to elucidate the effects of tillage practices and residue management, by removal of residue cover, on the dynamic properties of runoff and erosion. Six-row, 12.2 m long by 5.5 m wide, plots under CT or NT corn (Zea mays L.) for 9 years were used in this study. Plots had an average slope of 5.7% on a Grenada Silt Loam (Glossic Fragiudalf) soil. Rainfall simulations were conducted on a 10.7 m by 3.7 m area within each plot at a rate of 65 mm/h for one hour under natural antecedent soil-water conditions (dry run), followed by a 0.5 h simulation four hours later (wet run), and another 0.5 h application 30 minutes later (very wet run). The 10 treatments consisted of an incomplete 2x2x3 factorial arrangement of two tillage histories (CT and NT), two tillage levels (tilled and not tilled), and 3 residue management levels (residue left, residue removed just prior to simulated rainfall, and residue removed 1 year prior to simulated rainfall). The missing treatments being residue left under the NTh-tilled and CTh-not tilled. Dye releases were made at peak runoff to determine linear flow velocities. The time of runoff initiation (Ti), maximum runoff rates (ROmax), flow velocity, and maximum sediment concentration (Smax) were used to describe differences in runoff and erosion dynamics. Residue removal resulted in significantly sooner runoff with the NT system. There was a significant carry-over affect of residue removal with much sooner runoff initiation the subsequent year of removal. Maximum sediment concentrations were lower for the CTh land that is not tilled than the tilled despite the not tilled land experiencing sooner runoff and higher runoff rates. Tilling NTh land resulted in significantly lower sediment concentrations than tilling CTh land suggesting that the soil quality of NT is not immediately lost when tilled, but, these beneficial properties were fully lost within one year of residue removal.