Submitted to: ASABE Annual International Meeting
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2009
Publication Date: 6/22/2009
Citation: Cullum, R.F., Locke, M.A., Knight, S.S. 2009. How Conservation Reserve Program Affects Runoff and Nutrients in an Oxbow Lake Watershed. ASABE Annual International Meeting, Reno, NV, June 2009, Paper #097236. Interpretive Summary: Sediment and associated chemical pollutants in runoff from agricultural watersheds have been known to cause detrimental effects on receiving water bodies. How to reduce these sediments and chemicals from entering into lakes is being displayed in studies monitoring water quality from suggested best management practices at Beasley Lake watershed. Water quality at drain outlets from fields either in conservation tillage soybeans or in fields planted to trees was compared. Establishing trees within CRP adjacent to the oxbow lake reduced the concentration of sediments and nutrients leaving the watershed as compared to reduced-till crop management techniques. The reduced-till crop management practice resulted in average annual soil loss of 2.1 t/a soil loss, lower than the NRCS tolerance limit of 3 t/a. The impact of converting one third of the cropped area of Beasley watershed into trees reduced the sediment load leaving the watershed ten times lower than that from the cropped area, resulting in improved water quality in Beasley Lake.
Technical Abstract: A case study of Beasley Lake Watershed, located in the Mississippi Delta region of the U.S. was used to evaluate runoff from edge-of-field sites with row crop management practices and Conservation Reserve Program (CRP) sites with trees. Approximately one-third of the Beasley Lake watershed (280 ha) was converted from cropped land to CRP beginning in 2003, and the remainder of the cropland is managed for soybean, cotton, or corn production. Sub-drainage areas (1.2 to 6 ha) with similar topography and soil types were either cropped (three sites under reduced tillage crop) or placed in CRP (three CRP sites) and were instrumented in 2005 to collect water samples from field drainage slotted-inlet pipes during all surface runoff events. Runoff samples were analyzed for sediments and nutrients. This paper reports on runoff, soil loss, and nutrient loss for each site. Establishing trees within areas adjacent to the oxbow lake reduced the concentration of sediments and nutrients leaving the watershed as compared to reduced-till crop management techniques. The impact of converting the cropped area into trees has reduced the sediment load entering the lake by an order of magnitude, resulting in improved water quality in Beasley Lake.