Best Management Practices in the MS Delta: What Are We Learning?

Author(s): Kröger, R.; Prevost, J.; Cooke, T.

Agricultural best management practices (BMPs) can help reduce nutrient and sediment concentrations and loads leaving farm fields, which in turn can reduce negative impacts on downstream aquatic systems. For nearly three decades, significant federal investment in technical and financial assistance has been provided to implement farm BMPs. But few conservation programs attempt to estimate the amount of nutrient and sediment reduction resulting from cost-shared practices, let alone potential positive effect on local or regional water quality. This talk will encompass numerous ongoing and published scientific evaluations of BMPs within the MS Delta and the Lower Mississippi Alluvial Valley (LMAV). A review of BMPs within the LMAV highlighted only 18 articles (9 BMPs) that provided BMP efficiencies that met specific criteria of (a) row-crop agriculture, (b) clay/silt loam soils, (c) slopes 0-5%, and (d) occurred within the LMAV. The majority of the nine key BMPs for the LMAV provided significant nutrient reductions ranging from 15–100%. Field studies of innovative management practices such as low-grade weirs and slotted pipes have provided the very first nutrient reduction efficiency data for these structures in an agricultural field setting. Experimentally, it has been shown that weirs significantly increase nutrient reductions over conventionally drained systems. Field scale data on weirs is showing between 35-60% reductions for nitrate-N between inflow and outflow. Furthermore, the system documented a significant lag-effect that needs to be considered when evaluating BMP efficiencies. Slotted pipes have been quantified for the amount of sediment accumulation behind the structure. Observing sediment accumulation trends, (curvi-linear ; r2 = 0.76) and applying a Von Bertalanffy non-linear model for sediment accumulation through time for the evaluated sites, highlights that highest sediment accumulation occurs with 235 d following installation. These sediment accumulation rates can be translated to sediment volume and mass, and when multiplied by the total phosphorus concentration of the sediment provides a potential for evaluating performance for this specific BMP.
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Technical Sessions

1 Best Management Practices #1
2 Delta Water Assessment
3 Flood Assessment & Mgmt.
4 Wetlands
5 Watershed Mgmt. #1
6 Non-Point Source Assessment
7 Modeling
8 Water Quality
9 Best Mgt. Practices #2
10 Delta Water Conservation
11 Sedimentation
12 Storm Water
13 Watershed Mgt. #2
14 Public Water Systems
15 Surface Water Assessment & Evaluation

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