Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2015
Publication Date: 12/1/2015
Citation: Bosch, D.D., Potter, T.L., Strickland, T.C., Hubbard, R. 2015. Dissolved nitrogen, chloride, and potassium loss from fields in conventional and conservation tillage. Transactions of the ASABE. 58(6):1559-1571.
Interpretive Summary: Some of the benefits of conservation tillage include improved soil health and reduced surface runoff, sediment, and agrichemical loss. These practices are effective in part because they promote increased infiltration. In some landscapes this may result in increased movement of water in the subsoil as water accumulates in the soil. Transport of water soluble contaminants such a nitrate may result through the soil. Our investigation focused on determining whether use of strip-tillage, a common conservation tillage practice, during cotton and peanut production in the Atlantic Coastal region of the southeastern USA may increase subsurface transport of nitrogen, chloride, and potassium. Strip-tillage reduced surface runoff but increased subsurface water losses significantly. Total 5 year loading of nitrogen in subsurface flow from the strip-tillage treatment was double that from the conventional tillage treatment. Subsurface losses of nitrogen represented 18.4% of that applied for the strip-tillage system. Subsurface flow was the primary hydrologic pathway for dissolved nitrogen and potassium loss in both tillage systems in this landscape. Overall, strip-tillage was found to be an effective method for reducing surface runoff and associated soluble losses, but increased infiltration with this practice may significantly increase subsurface losses.
Technical Abstract: Losses of soluble nutrients from cropland and their transport to surface and groundwater are a continuing water quality concern. In this study we evaluated tillage impact on dissolved losses of ammonium (NH4-N) and nitrate nitrogen (NO3-N), chloride (Cl), and potassium (K) during rotational cotton and peanut production. Tillage treatments were strip-tillage (ST) and conventional-tillage (CT). Tillage treatments were uniformly applied within two 0.6-ha fields located on a moderately sloping hillslope in the southern Atlantic Coastal Plain region of south-central Georgia (USA). Tile drains were installed at the base of the slope of each field to capture lateral subsurface flow. During the 5-yr study, annual precipitation ranged from 910 to 1488 mm, with an annual average of 1201 mm. Annual surface runoff averaged 199 mm from the CT field while the ST averaged 137 mm, 17 and 11% of annual rainfall respectively. Annual average surface runoff loadings of NH4-N, NO3-N, and Cl from the ST treatment were found to be significantly less than that from the CT treatment. Total 5 year loads of N (NH4-N and NO3-N) in surface runoff from the CT treatment was 8.3 kg ha-1 while it was 5.6 kg ha-1 from the ST, equivalent to 1.5% of the total N applied for the CT and 1.0% of that applied for ST. Annual subsurface flow averaged 146 mm for CT and 254 mm for ST, 12% and 21% of annual precipitation respectively. Annual average subsurface flow loadings of NH4-N, NO3-N, and K from the ST treatment were significantly greater than from the CT. Total 5 year loading of N (NH4-N and NO3-N) in subsurface flow from the CT treatment was 45 kg ha-1 and 99 kg ha-1 from ST, equivalent to 8.3% of the total N applied to CT and 18.4% of that applied for ST. Data showed that subsurface flow is the primary hydrologic pathway for dissolved nitrogen and potassium loss in both tillage systems. Overall, ST was found to be an effective method for reducing surface runoff and associated soluble losses, but increased infiltration with this practice may significantly increase subsurface losses.