Project Number: 6602-12130-001-00
Project Type: Appropriated

Start Date: Sep 07, 2006
End Date: Sep 06, 2011

Objective:
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.

Approach:
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.