Tillage and slope position impact on field-scale hydrologic processes in the South Atlantic Coastal Plain

There is widespread interest in increasing conservation tillage use during row crop production. However, long-term hydrologic data are needed to better evaluate the potential benefits of conservation tillage. To that end, hydrologic monitoring was conducted for 11 years on a 1.2 ha hillslope located in the Atlantic Coastal Plain region of south central Georgia, USA. The site was equally divided between two tillage treatments, conventional-tillage (CT) and strip-tillage (ST), with cotton and peanut produced in rotation. Each tillage block was divided into three 0.2 ha plots to evaluate runoff as a function of tillage and slope position. Soil texture and hydraulic characteristic data were quantified to evaluate potential impacts on hydrologic processes including runoff, infiltration, and lateral subsurface flow. Surface runoff from CT averaged 22% of annual precipitation while that from ST averaged 13%. When paired by tillage and landscape position, annual runoff from ST was significantly less than annual runoff from CT (p = 0.025). Monthly surface runoff from CT was consistently greater than that from ST, particularly during May through August. Increased infiltration as a consequence of the reduced tillage led to significantly greater average annual subsurface losses from ST (19%) than from CT (10%) (p = 0.025). Results indicated that slope position and textural differences may also have influenced site hydrology. Plots at the top of the landscape where finer soil textures were observed produced greater runoff than plots at lower landscape positions where coarser textures were observed. In summary, the ST cotton/peanut rotation can be expected to significantly reduce runoff but increase lateral subsurface flow. As a consequence, water budgets from the two tillage systems were essentially equal. Similar decreases in surface runoff and increases in lateral subsurface flow can be expected to occur in landscapes in the Atlantic Coastal Plain Region where strip tillage is adopted.

► Hydrologic monitoring was conducted for 11 years on a 1.2 ha Atlantic Coastal Plain hillslope.
► Conventional-tillage runoff averaged 22% of annual precipitation and strip-tillage averaged 13%.
► Strip-tillage annual runoff was significantly less than that from conventional-tillage.
► Increased infiltration led to higher average annual subsurface losses from strip-tillage.
► Water budgets from the two tillage systems were essentially equal.