Submitted to: Clean Water Clean Environment 21st Century Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/5/1995
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Influences of different farming practices on water quality have been studied in limited areas and often inferred from well monitoring programs. A study was designed within the Walnut Creek watershed south of Ames, IA, to evaluate the onsite and offsite impact of different farming practices. Extensive monitoring of surface runoff, stream flow, tile drainage, and shallow wells for herbicide and nitrate-nitrogen concentrations has been conducted within the watershed since 1990. Coupled with the water quality monitoring have been measurements of water flow, soil characteristics, precipitation amounts, meteorological data, and farming practices to provide a complete picture of the watershed. For each field within the watershed, the crop planted, herbicide used, rate and amount, fertilizer used, type, rate and amount, and type of tillage practice have been recorded for each year since 1991. Concen- trations of atrazine, alachlor, metribuzin, and metolachlor in the surface runoff are dependent upon the time between application and a runoff event. Tillage practices that decrease the chance of runoff by increasing infiltration and water storage in the profile reduce the loss of atrazine and metolachlor from fields. The total amounts of atrazine and metolachlor found in the tile drainage water and stream flow represent less than 0.5% of the amount applied throughout the watershed. Nitrate amounts lost in the tile drainage and stream flow represent large portions of the amount applied. Over the four years, the losses ranged from 40 to 115% of the amount applied. Herbicide concentrations were nondetectable and nitrate-nitrogen concentrations were between 1 and 2 ppm in wells. Farming practices can be modified to have a positive impact on water quality.