Effects of Field and Edge-of-Field Conservation Practices On Runoff Water Quality in Mississippi Delta Cotton.

A non-irrigated cotton field study was established in 2003 on the Delta Branch Experiment Station, Stoneville, MS. The experimental area (ca. 2.5 ha) was arranged in a randomized complete block design with three blocks (18 experimental units, 6 in each block). Combinations of within-field practices and edge-of-field BMPs within each block include: (1) reduced tillage (RT), no cover crop (NCC), with no edge-of-field BMP (NEBMP); (2) RT, NCC, with 1-m stiff grass barrier using switchgrass; (3) RT, NCC, with 12-m vegetative filter strips; (4) no-tillage, NCC, NEBMP; (5) RT, rye cover crop, NEBMP; and (6) a conventional tillage, NCC, NEBMP. Each of the 21 experimental units is 150-m long by 8-m wide and equipped with automated surface runoff sampling equipment that was used to monitor runoff from 2007 to 2011. Composite runoff samples were collected during runoff events to determine sediment and nutrient (N and P)losses. Conservation practices that increased residue cover on the field (NT, RT, rye cover crop) and that provided an edge-of-field barrier (stiff grass; vegetative filter strip) reduced sediment loss in runoff. Also, nutrients (TKN and TP) that were associated with sediment were reduced. However, nutrient loss associated with the runoff solution phase (soluble TKN, TP) tended to increase under conservation management. Also, TOC loss in runoff was higher under conservation management.