2007 Annual Report 1a.Objectives (from AD-416) Assess the dissipation, fate and transport of commonly used broadcast herbicides and fungicides in soil as a function of tillage management. Quantify the affect of cropping and tillage systems on soil organic carbon, specifically how changes in soil organic carbon impacts pesticide and nitrogen dynamics, erosion mechanics, sediment generation, and carbon loss associated with extreme events. This objective contributes to the CLR GRACEnet project. Measure hydrologic components (rainfall, runoff, infiltration, soil water content and redistribution following rainfall and irrigation, lateral subsurface flow, plant water use and evapotranspiration so that differences in plant water use and evapotranspiration so that differnces in plant available water as a function of cropping, tillage systems, soil compaction, and rooting density can be quantified. 1b.Approach (from AD-416) Plots located at a UGA research farm in Tift County, GA (N 31o 26', W 83o 35') will be a primary resource for all aspects of the study. Plots were established in 1998 by dividing a 1.8-ha parcel into six 0.15-ha and one 0.4-ha sub-plots. Since study inception the three 0.15-ha plots on the northern side of the area have been maintained under conventional tillage management. This involves discing, ripping and bedding each spring leaving a residue free seed bed for planting. The other three 0.15-ha plots have been in strip-tillage. In this case crops are planted into 15-cm wide strips tilled into cover crop residue mulch. Rye (Secale cearale L.) cover crops sown each fall on all plots are killed each spring with herbicides. The 0.4-ha plot at the top of the slope was divided equally across the slope by the two tillage practices. It has and will continue to be used for rainfall simulation investigations. During construction, each of the 0.15-ha plots was surrounded by a 0.6 m earthen berm that directs surface flow to metal H-flumes installed at the downslope corners of each plot. Flumes were equipped with pressure transducers and rating curves were developed. Flow (as a function of changes in pressure) is recorded during runoff events. Flow weighted samples are also collected using autosamplers. Additionally two separate loops of 15-cm diameter tile drain were installed at the surface of the argillic horizon with one loop surrounding the 3 strip- and one the 3 conventional-tillage 0.15-ha plots. H-flumes were installed on tile outlets to measure flow and refrigerated autosamplers are currently being installed so that water samples can be systematically collected for pesticide and nutrient analysis. Monitoring wells were also constructed at up- and downgradient locations of each plot so that shallow groundwater hydraulics and water quality could be monitored. A climate station at the site continuously measures precipitation, wind speed and direction, relative humidity, air temperature, vapor pressure, and solar radiation. Data are used to estimate crop evapotranspiration rates. Calibration on the instruments will be checked every year. Evapotranspiration estimates will be used to develop hydrologic budgets for the crops grown at the site and to make comparisons to the evapotranspiration rates calculated from stem-flow measurements. A solid set irrigation system capable of applying uniformly water to each plot was installed for the study. 4.Accomplishments Rainfall intensity pattern impacts on runoff and pesticide, nutrient, sediment, and organic carbon loss during field-based rainfall simulations - Reduced tillage systems offer a best management tool for sustained row crop production in many agricultural settings. One of the most effective ways of evaluating tillage impacts is through use of field-based rainfall simulations. Typically rainfall is applied at a constant rate during simulations; however natural rainfall patterns are rarely if ever constant. Implications were evaluated in field-based simulations in which tillage impacts on runoff, sediment, organic carbon, nutrient and runoff of two herbicides were compared. Rainfall was applied to plots established in a cotton-rotation at constant rate versus a variable rate pattern that is representative of spring storms in the southern Atlantic Coastal Plain of Georgia (USA). Studies showed that use of a variable pattern is technically feasible and that processes controlling water storage and sediment, carbon, nutrient and herbicide losses from soil would be better understood if variable rainfall intensity patterns derived from natural rainfall were utilized in rainfall simulation studies. This research addresses Problem Areas 2(Soil Management to Improve Soil Structuure and Hydraulic Properties), 3(Soil Carbon Dynamics, Management, and Measurement Tools), 5 (Adoption and Implementation of Soil and Water Conservation Practices and Systems), 7(Managing Pesticides in Soils), and 8 (Control of Soil Erosion) of the 202 National Program. Long-term assessment of hydrologic, soil, and water quality response to conservation tillage in the southern Atlantic Coastal Plain - Sustainable production of cotton, peanut and other crops in the region requires that growers minimize negative environmental impacts and reduce costs through water conservation. To this end, conservation practices such as strip-tillage, may offer significant benefit. Seven years of data were complied from a comprehensive tillage study in south-central Georgia. Results showed that on average strip-till provided equivalent crop yields combined with about 2 times less surface runoff and erosion when compared to conventional-tillage. Reduced herbicide loss with strip-till by up to 10-fold was also documented. The research has quantified the benefits of strip-tillage and will likely promote increased rates of adoption of the practice by providing data that allows direct cost-benefit analysis of tillage practices. This research addresses Problem Areas 2(Soil Management to Improve Soil Structuure and Hydraulic Properties), 3(Soil Carbon Dynamics, Management, and Measurement Tools), 5 (Adoption and Implementation of Soil and Water Conservation Practices and Systems), 7(Managing Pesticides in Soils), and 8 (Control of Soil Erosion) of the 202 National Program. Herbicide incorporation by irrigation and tillage impact on runoff loss - To reduce herbicide runoff risk, cotton and peanut farmers in the Atlantic Coastal Plain are encouraged to irrigate soon after application the herbicides are applied. In theory the practice should effectively reduce runoff losses. To quantify impacts, we conducted rainfall simulations in a field in a cotton-peanut rotation in south central Georgia (USA). We found that herbicide runoff was up to two times less from plots that were irrigated prior to a rainfall event compared to those that were not. Studies also showed that the practice’s efficacy was strongly impacted by tillage management and herbicide properties. When a commonly used conservation-tillage practice, strip-tillage, was used, whether plots were irrigated or not had little impact on runoff of an herbicide that has low water solubility and high capacity for adsorption by soil. These findings will be useful to growers, since it will help them determine when irrigation will be most useful to reduce herbicide runoff losses. This research addresses Problem Areas 2(Soil Management to Improve Soil Structuure and Hydraulic Properties), 3(Soil Carbon Dynamics, Management, and Measurement Tools), 5 (Adoption and Implementation of Soil and Water Conservation Practices and Systems), 7(Managing Pesticides in Soils), and 8 (Control of Soil Erosion) of the 202 National Program. 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 2 Number of newspaper articles and other presentations for non-science audiences 5 Review Publications Davis, J.G., Truman, C.C., Kim, S.C., Ascough II, J.C., Carlson, K. 2006. Antibiotic transport via runoff and soil loss. Journal of Environmental Quality. 35:2250-2260. Potter, T.L., Truman, C.C., Bosch, D.D., Strickland, T.C., Franklin, D.H., Bednarz, C.W., Webster, T.M. 2006. Combined Effects of Constant Versus Variable Intensity Simulated Rainfall and Reduced Tillage Management on Cotton Preemergence Herbicide Runoff. Journal of Environmental Quality. 35:1894-1902. Cobb, J., Mattice, J., Senseman, S., Dumas, J., Mersie, W., Riley, M., Potter, T.L., Mueller, T., Watson, E. 2006. Pesticide Extraction Efficiency of Two Solid Phase Extraction Disk Types After Extraction and Shipping. Journal of Association of Official Analytical Chemists International. 89:903-912.