1 REDUCING RUNOFF VOLUME AND CONCENTRATIONS OF PHOSPHOROUS AND ATRAZINE WITH GYPSUM AMENDMENT

Erosion control can be achieved by reducing runoff volume using soil amendments that improve infiltration and prevent particle detachment and transport. Effective soil erosion control can be achieved by a number of means, however, water quality may still be impaired by removal of soluble nutrients and pesticides. We hypothesized that addition of an electrolyte source (gypsum) to the soil/air/water interface not only could achieve erosion control, but could also reduce the concentration of soluble reactive phosphorous (SRP) and atrazine (ATz). We tested this hypothesis in a two year rainfall simulator study on field plots untreated and treated with recycled drywall gypsum (surface applied at 1 MT/ha) following addition of ATz containing herbicides. We applied rainfall to replicated plots with 5 % slope at a target rate of 64 mm/hr until steady state runoff was achieved and runoff samples were collected in intervals of 5 minutes to measure sediment, SRP and ATz losses. A control, gypsum and a poultry litter treatment were all trimmed of corn grown in a no-tillage system prior to rainfall. We found that addition of gypsum not only reduced runoff volume and sediment loss but also reduced the concentration of SRP especially in the poultry litter treatment and ATz. Total losses of both SRP and ATz were reduced by a combination of reduced runoff volumes and concentrations. Addition of gypsum to critical areas in fields treated with soluble ATz or poultry litter appears to be a viable management strategy to reduce off-site water quality concerns