# Presentation: 677933

## Protecting Surface Water from Atrazine Runoff

- Dr. Richard S. Fawcett
- Fawcett Consulting
- On behalf of the Triazine Network

## Atrazine Benefits

- Effective weed control at lower cost
- Increased yield: 5.7 bushels/acre in 20-year university trial assessment
- Facilitates adoption of conservation tillage
- Soil erosion reduced 33% from 1982-2001
- No-till reduces pesticide runoff by 70%
- Fuel savings of 89 million gallons annually in U.S. corn production

## Farmers are Protecting Surface Water

- Atrazine Remains the Most Widely Used Corn Herbicide
- Yet Atrazine Concentrations in Surface Water Have Declined Over the Last Decade and Continue to  Decline

## Actions by Growers Have Succeeded

- Followed Label Changes
- Rate reductions
- Set backs where runoff enters streams
- Label Harmonization among registrants during reregistration
- Adopted Voluntary BMPs
- Conservation tillage
- Postemergence applications
- Conservation buffers

## Monitoring Studies Confirm Decline

- USGS: 50% decline in median concentrations 1989-1995
- NAWQA: significant reduction in stream residues 1992-2001
- Iowa DNR: statistically significant decline for all surface water category
- Intensive monitoring of drinking water reservoirs shows consistent decline

## Is atrazine harming aquatic ecosystems by reducing photosynthesis in algae and aquatic plants?

## Atrazine and Aquatic Ecosystems

- If a reduction in algae and aquatic plant growth due to atrazine were to adversely affect an aquatic community...
- Then current levels of aquatic plant growth would have to be deficient.
- However, according to EPA Office of Water, most rivers and lakes across the Corn Belt have very excessive aquatic plant growth, not too little.

## Atrazine and Aquatic Ecosystems

- 2000 National 305(b) Report: excessive nutrients most common pollutant affecting lakes, reservoirs, and ponds - 50% of impaired waters
- EPA published Ecoregional Nutrient Criteria
- Regional Technical Assistance Groups (RTAGS) also developing proposed criteria
- States must set enforceable nutrient and chlorophyll-a standards

## Atrazine and Aquatic Ecosystems

- Throughout the Corn Belt, N, P, and chlorophyll-a concentrations are routinely 2 to 4 times EPA criteria
- In Iowa, all but one of 131 lakes exceeded proposed standards for N & P with some lakes 20-fold above standards
- In Iowa, 98 of 131 lakes exceeded chlorophyll-a standards

## Slide 10

## Atrazine and Aquatic Ecosystems303(d) Impaired Waters

- Illinois: 57% of impaired waters list excessive nutrients and/or algae as cause
- Iowa: 50% of impaired lakes list excessive algae as cause

## Atrazine and Aquatic Ecosystems...

- 	Algae and plant growth is excessive, not sub-optimal in most rivers, lakes, and ponds in regions where atrazine is used

## Conclusions

- Atrazine remains a valuable tool for farmers, used on more acres than any other corn herbicide
- Atrazine provides many benefits, including increased yield and facilitating adoption of conservation tillage
- Conservation tillage reduces erosion and runoff of nutrients & pesticides, and saves fuel
- Farmers have abided by water-protecting label changes

## Conclusions (continued)

- Farmers have adopted additional voluntary  BMPs
- Atrazine concentrations in surface water are low and continue to decline
- Algae and plant growth is excessive, not sub-optimal in most rivers, lakes, and ponds in regions where atrazine is used
- Atrazine is unlikely to have detrimental effects