Runoff and nutrient losses from conventional and conservation tillage systems during fixed and variable rate rainfall

Authors: Endale, Dinku; Schomberg, Harry; TRUMAN, CLINT - Syngenta; FRANKLIN, DORCAS - University Of Georgia; TAZISONG, IRENUS - Alabama A & M University; Jenkins, Michael; FISHER, DWIGHT - Az Statistics

Submitted to: Journal of Soil and Water Conservation Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/14/2019
Publication Date: 11/15/2019
Citation: Endale, D.M., Schomberg, H.H., Truman, C., Franklin, D., Tazisong, I., Jenkins, M., Fisher, D. 2019. Runoff and nutrient losses from conventional and conservation tillage systems during fixed and variable rate rainfall. Journal of Soil and Water Conservation Society. 74(6):594-612. doi:10.2489/jswc.74.6.594.
DOI: https://doi.org/10.2489/jswc.74.6.594

Interpretive Summary: Tillage and fertilization choices have positive or negative implications on farming system outcomes such as productivity and ecosystem services. ARS scientists in Watkinsville, GA, and university colleagues, determined runoff amount and quality from corn plots managed under conventional tillage (CT) and no-till (NT) fertilized with conventional fertilizer (ammonium nitrate) or poultry litter on a Cecil soil, using constant rate (CR; 2004) and variable rate (VR; 2005) rainfall simulations. In 2004, 55.8% of the simulated rainfall was partitioned into runoff from CT compared with 9.7% from NT. In 2005, 42 to 60% was partitioned into runoff with no difference among treatments. Sediment loss was 11-fold greater from CT compared with NT in 2004. In 2005, there were no differences among treatments. Regarding quality of runoff, compared with CT, NT had greater loads (calculated as concentration x runoff volume) for ammonium-nitrogen and nitrate-nitrogen in both years, and dissolved reactive and total phosphorus in 2005. Our results confirm that 12 yr of continuous no-till on a Cecil soil, representative of much of the Southern Piedmont, is far superior to conventional tillage for reducing runoff and sediment loss. The results also suggest that if future climate projections for our region are realized, which call for larger and more intense storms, then, more runoff and sediment loss will be expected from Piedmont soils and that a greater percentage would be expected from CT systems. This points to the need for continued innovations in agricultural management practices, like NT, to limit offsite losses of sediment and nutrients from agricultural fields, particularly those receiving poultry and other animal manure.

Technical Abstract: Tillage system management directly impacts soil functions that indirectly impacts ecosystem services, sustainability, and economic productivity. Conventional tillage (CT) and no-till (NT) systems were evaluated for differences in runoff amount and quality from corn plots supplied with conventional fertilizer (CF - ammonium nitrate) or poultry litter (PL) on a Cecil soil (Ultisol) near Watkinsville, GA, using rainfall simulations. A constant rate (CR) was applied in 2004 and a variable rate (VR) in 2005 (CR: 57 mm hr-1 for 60 min; a10-yr return period. VR: in mm hr-1, increasing from 1 at the start to 58 at 12 min; 160 at 20 min; then decreasing to 60 at 35 min; and 23 at 60 min providing 57mm rain in one hr). Tillage and tillage x fertilizer interactions had significant effects on total runoff and sediment loss in 2004 but not in 2005. Fertilizer did not have a significant effect in either year. In 2004, 55.8% of the simulated rainfall was partitioned into runoff from CT compared with 9.7% from NT. In 2005, 42 to 60% was partitioned into runoff with no difference among treatments. Sediment loss was 11-fold greater from CT compared with NT in 2004 (919 vs 82 g). In 2005, sediment loss varied between 755 and 2174 g with no difference among treatments. Tillage and tillage x fertilizer interactions had significant effects on total load for ammonium-nitrogen (NH4-N) and nitrate-nitrogen (NO3-N) in both years and dissolved reactive and total phosphorus (DRP and TP) in 2005. Significant fertilizer effect was evident for loads of NH4-N in 2005 and NO3-N and TP in both years. Our results confirm that 12 yr of continuous no-till on a Cecil soil, representative of much of the Southern Piedmont, is far superior to conventional tillage for reducing runoff and sediment loss. The results also suggest that if future climate projections for our region are realized, which call for larger and more intense storms, then, more runoff and sediment loss will be expected from Piedmont soils and that a greater percentage would be expected from CT systems. This points to the need for continued innovations in agricultural management practices, like NT, to limit offsite losses of sediment and nutrients from agricultural fields particularly those receiving poultry and other animal manure.