SOIL PROCESSES IN PRODUCTION SYSTEMS THAT INCORPORATE BIOFUEL FEEDSTOCKS INTO SOUTHEASTERN AGRICULTURE
Location: Southeast Watershed Research
Title: Tillage and slope position impact on field-scale hydrologic processes in the South Atlantic Coastal Plain
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 15, 2012
Publication Date: June 11, 2012
Citation: Bosch, D.D., Truman, C.C., Potter, T.L., West, L.T., Strickland, T.C., Hubbard, R.K. 2012. Tillage and slope position impact on field-scale hydrologic processes in the South Atlantic Coastal Plain. Agricultural Water Management. 111:40-52. Available: http://dx.doi.org/10.1016/j.agwat.2012.05.002.
Interpretive Summary: Reduced energy cost, improved soil, and reduced soil erosion have been cited as some of the reasons for the dramatic increase in conservation tillage systems throughout the United States. While improved infiltration of rainfall into the soil is also often observed in these systems, hydrologic benefits of reduced tillage systems are often difficult to quantify. This study examines eleven years of data from an Atlantic Coastal Plain study site in the Southeastern U.S. and characterizes hydrologic response of the site. Results indicate that conservation tillage can lead to a 59% reduction in surface runoff. On an annual basis, the reduced surface runoff is offset by a 90% increase in subsurface water losses. However, because little subsurface loss occurs during the summer crop growing season, the conservation tillage system provides beneficial increases in soil water during this critical period of the year. These results will help guide proper management of these systems.
There is widespread interest in increasing conservation-tillage use during row crop production. Hydrologic monitoring was conducted for 11 years on a 1.2 ha hillslope located in the Atlantic Coastal Plain region of south central Georgia. 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. 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 (p=0.01) annual runoff from CT. Monthly runoff from CT was consistently greater than that from ST, particularly during June through August. Increased infiltration as a consequence of the reduced tillage led to higher average annual subsurface losses from ST (19%) than from CT (10%). Differences when paired by years were significant (p=0.05). Landscape and textural differences also influenced site hydrology, with the top of the landscape where finer soil textures were observed producing greater runoff than lower landscape positions where coarser textures were observed. The 11 years of data provide quantitative examination of hydrologic and physical differences that can be expected from landscapes of this type. Strip-till in the 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.