Mississippi Delta MSEA Volume 1, Issue 1, Page 2

MISSISSIPPI DELTA

How will the Mississippi Delta MSEA be conducted?

Three oxbow lake watersheds will each be instrumented to automatically collect field runoff at selected locations. One watershed will serve as a control with only conventional farming practices in use and the other two watersheds will have alternative farming systems implemented on them, each to different degrees. The alternative systems will be composed of combinations of BMPs including but not limited to conservation tillage, grass filter strips and waterways, slotted-board risers, and improved agrichemical application technology. One runoff gauging station at each lake watershed will have multiple automatic water samplers and will facilitate both instantaneous (time proportional) and composite (flow proportional) sampling. Other gauging stations will be for composite sampling only. Runoff samples will be separated into sediment and water phases and measurements will include nutrients, pesticides and metabolites, total organic carbon (TOC), sediment organic carbon, sediment concentration and particle size distribution, sediment toxicity (via bioassay), and coarse particulate organic matter.

The lakes themselves will be instrumented for water quality and primary productivity sampling prior to and after implementation of BMPs on adjacent lake watersheds. Water quality will be sampled weekly with three profile samples taken within the body of each lake and one surface sample collected at each lake outlet and at some distance downstream (if applicable). Water quality samples will be analyzed for physical [temperature, conductivity, secchi visibility (turbidity), etc.] and chemical (nutrients, pesticides and metabolites, pH, dissolved oxygen, solids, etc.) characteristics. Concentrations of plankton and chlorophyll as well as primary productivity will be measured at the same three water quality profile sites in each lake. Macroinvertebrates will be sampled monthly along two transects for each lake. After intensive initial sampling and prior to implementation of BMPs, lakes will be "renovated" with rotenone and restocked with centrarchid fishes (largemouth bass, bluegill) at appropriate ratios. Researchers will then quantify fisheries productivity and sustainability of the lakes.

Oxbow lake watersheds will also be instrumented with numerous observation wells to determine shallow ground water quality before and after BMP implementation. Observation well depths will range from just below the root zone down to water table and analysis of shallow groundwater samples will be similar to that of surface water samples.

Very important specific research efforts in the project include: sampling and analysis of lake sediments for residual and current-use pesticides; quantifying the role of soil cracks (very pronounced in many Delta soils) in agrichemical transport in runoff and leaching to shallow groundwater; monitoring selected indicator aquatic and terrestrial organisms in the lake ecosystems for pesticide residues; evaluating ARS-developed water quality models in terms of their applicability to the Mississippi Delta; quantifying agrichemical transport and transformations in riparian zones, grass filter strips, and slotted-board riser impoundments/sediment ponds; and comprehensive assessment of socioeconomic factors related to farmer acceptance and adoption of alternative farming practices.

Improved agrichemical application technology will consist of timing, amount, and formulation components. The timing component will likely involve adjusting the timing of agrichemical applications based upon the probability of rainfall in the daily and 7-day weather forecast models for the study sites. The amount component will consist of applying herbicides ULV at reduced rates with a specially-developed air-assist spray system equipped with weed sensor technology. The formulation component involves such things as substituting slow-release nitrogen fertilizer for conventional nitrogen fertilizer at recommended rates based on soil tests. Site-specific agrichemical application (prescription farming) using a geographical information system (GIS) and a global position system (GPS) is also planned.

Prior to and after implementation of BMPs on lake watersheds, soil samples will be collected for comprehensive chemical and biological characterization including organic matter (OM), pH, herbicide sorption parameters and biodegradation rates, microbial biomass, baseline microbial populations, and enzyme activities.

The overall plan is to develop a group of practical, economically-feasible BMPs that farmers/operators/producers will use to save the soil and clean up the hundreds of oxbow lakes throughout the Mississippi Delta.