Why evaluate nitrate losses from watersheds?

1. Why evaluate nitrate losses from watersheds? • Potential health risks to public and private water supplies • Eutrophication • Hypoxia - Deficiency in the amount of oxygen reaching body tissues. • TMDLs

2. Why atrazine? • Risk to human and aquatic life forms • Interim Reregistration Decision (IRED) • Memorandum of agreement • USEPA standard • maximum annual average of 2.6 ppb • 90-day average of 37.5 ppb of atrazine and all triazine compounds

3. Probability potential of atrazine

4. Atrazine • Herbicide widely used to control numerous broad-leaved weeds and is primarily applied to corn • Atrazine is one of the most widely used herbicides in the United States with 62% of corn acreage nation wide being treated and 78% of the corn acreage in Indiana • The extensive use of atrazine as a pre-emergence herbicide to control broad-leaf weeds has the potential to impact aquatic life and human health

5. Atrazine • Atrazine has the potential of causing effects within an ecosystem, disrupting the normal processes of some species. • According to Wiegand et al. (2001), atrazine at concentration levels between 10 and 20 mg/L can cause retardations in organogenesis, a slow down of movements, and functional disturbances of the heart • Atrazine has also been known to induce hermaphroditism at 0.1 ppb in American Leopard Frogs (Hayes et al., 2003

6. Atrazine Studies • One study on human health in Minnesota measured children’s exposure to pesticides through urine samples, where 102 children between the ages of three and thirteen years were studied. Atrazine metabolites were detected 4% of the time (Adgate et al., 2001). • USEPA standard of a maximum annual average of 3.0 ppb or a 90-day average of 37.5 ppb of atrazine and all triazine compounds

7. Atrazine Mobility • Transport mechanisms of atrazine are primarily in solution with water; there is little adsorption on sediment and observed adsorption seems reversible • The high mobility of atrazine and its persistence leads to the concern for human health

8. NAPRA • National Agricultural Pesticide Risk Analysis (NAPRA) • Developed by USDA NRCS • Extended by ABE Purdue • Designed to assess risk of pesticide loss to ground or surface water as a result of various crop-tillage management practices

9. The NAPRA Process • Analysis of the environmental risk associated with pesticide management decisions • Quantify environmental benefits of alternative management strategies • Assist farmers in striking a balance (economic vs. environment) in their pest management decisions

10. Key GLEAMS/NAPRA Features • GLEAMS model • Weather database • Soil Databases • Risk component • WWW interface

11. Rainfall Runoff Seepage/Percolation

12. INPUT INTERFACE • Soil • Type or Geographic Location • Climate • Weather Station • Crop • Type • Planting/Harvesting Date

13. INPUT INTERFACE • Pesticide and nutrients • Type • Application Rate • Management Practices • Website: http://danpatch.ecn.purdue.edu/~napra/TCT/mainFrame.html

15. OUTPUT TYPES • Source • Percolation, Runoff or Sediments • Time • 90-Day Maximum or Annual • Units • Loading (g/ha) or Concentration (ppb)

16. OUTPUT INTERFACE 3 ppb Pesticide in Runoff (ppb) Time

17. OUTPUT INTERFACE Pesticide in Runoff (ppb) 3 ppb 80% Probability of Exceedance

20. Summary • GLEAMS/NAPRA approach potentially spans scales from regional to local • GLEAMS/NAPRA approach allows accounting for management • WWW and databases make NAPRA easy to use