Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/31/2015
Publication Date: 7/26/2015
Citation: Bosch, D.D., Potter, T.L., Strickland, T.C., Hubbard, R.K. 2015. A comparison of dissolved inorganic nitrogen, chloride and potassium loss in conventional and conservation tillage. ASABE Annual International Meeting, July 26-29, New Orleand, LA.
Technical Abstract: 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 was evaluated. Tillage treatments were strip-tillage (ST) and conventional-tillage (CT). Winter cover crops were used in both tillage systems. The tillage treatments were uniformly applied within two tile-drained 0.6-ha fields located on a moderately sloping hillslope in the southern Atlantic Coastal Plain region of south-central Georgia (USA). Each field was subdivided into three 0.2 ha plots. H-flumes installed on tile outlets and downslope corners of each 0.2-ha plot were used for flow measurement and sample collection. During the 5-yr study, annual precipitation ranged from 910 to 1488 mm, with an annual average of 1201 mm. CT–field annual surface runoff averaged 291 mm while the ST averaged 181 mm, 24 and 15% of annual rainfall respectively. Nitrate N concentrations in surface runoff averaged 0.65 mg L-1 for CT and 0.64 mg L-1 for ST. Because of the low variability in concentrations, surface runoff loads closely tracked surface runoff volumes. Annual average surface runoff loading of NO3-N and Cl from the ST treatment was found to be statistically different from that of the CT treatment. Total 5 year loads of inorganic 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 fields were significantly greater than from the CT fields. Total 5 year loading of inorganic 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 fields and 18.4% of that applied for ST. Data showed that subsurface flow is the primary hydrologic pathway for dissolved inorganic nitrogen and potassium loss in both tillage systems. Overall, strip-tillage was found to be an effective method for reducing surface runoff, but increased infiltration with this practice may substantially increase subsurface losses. This introduces new challenges related to nitrogen and potassium management in reduced tillage systems in the region.