Runoff Amount and Quality As Influenced By Tillage and Fertilizer Management Choices in a Cecil Soil.

Tillage and fertilizer choices and their interactions have varying impacts on levels and qualities of runoff from agricultural fields. We quantified runoff, sediment loss, concentrations and loads of ammonium-nitrogen (NH₄-N), nitrate-nitrogen (NO₃-N), dissolved reactive phosphorus (PO₄-P) and total phosphorus (TP) from a Cecil soil near Watkinsville, GA, under rainfall simulation in 2004 (constant rate) and 2005 (variable rate). Two tillage (conventional tillage CT and no-tillage NT; main plots) and two fertilizer treatments (mineral fertilizer CF and poultry litter PL; subplots) were arranged in a randomized complete block (split plot) design with three replications. Rainfall simulation was conducted on 6.6 ft by 9.8 ft section of each of the twelve 30 ft by 100 ft plots for 60 minutes. Runoff volume in 2004 was greater from CT than NT (x 6 to 8 for means). Differences were much smaller in 2005 (x 1.1 to 1.3). Sediment mass in 2004 was greater from CT than NT (x 10 to 13). We have no data for 2005. In both simulations, nutrient concentration and load was much larger from NT than CT (x 1.2 to 66); NO₃-N concentration and load was much larger from CF than PL (x 3 & 49 for concentration and x 22 & 8.6 for load); and phosphorus load was greater from PL than CF (x 1.3 & 2.3). Concentrations of NH₄-N and PO₄-P were greater from CF than PL in 2004 (x 2.8 & 1.8) but reversed in 2005 (x 5.4 and 2.3). Load of NH₄-N was greater from CF than PL in 2004 (x 1.4) but reversed in 2005 (x 4.8). The treatments influenced values of the considered variables.