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Ag leaders reject USGS nitrate study

Published on February 14, 2013 3:01AM

Last changed on March 14, 2013 8:49AM

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Dairy leaders point to urban areas as source of problem


Capital Press

Idaho farm leaders are questioning the results of a U.S. Geological Survey study that singles out agriculture for an anticipated increase in nitrate levels in groundwater.

The report lays much of the blame for increased nitrate levels in southcentral Idaho at the feet of farmers and dairies.

"I know other things are contributing to the nitrate problem, but they always want to go (after) farming first," said dairyman Steve Ballard, president of Gooding County Farm Bureau.

Ballard said dairies and farmers in the area have taken a lot of proactive steps to reduce nutrient leeching, and he doesn't believe agriculture is the main problem.

"As a dairyman and a farmer, I surely don't want to damage the water supply for my cows," he said. "I think the issue needs to be studied more."

The report identifies inorganic fertilizer, cattle manure and legume crops as the main sources of nitrates in groundwater in the mid-Snake region of southcentral Idaho.

Working with existing data on fertilizer and manure application, the report used a computer model to simulate changes in nitrate concentrations over time.

It found that nitrate concentrations would continue to increase over time even if nitrogen input remained constant, eventually exceeding the Environmental Protection Agency's threshold for safe drinking water in some areas.

That doesn't mean farm and dairy management plans aren't working, its authors say.

"It's just that it takes time for the results to show up in the aquifer," said Ken Skinner, USGS project chief for this study.

The data the model used show that most nitrate hot spots are near Twin Falls south of the Snake River canyon, while the dairies are north of the canyon, said Givens Pursley attorney Hugh O'Riordan, who represents IDA on this issue.

"Why doesn't the study include the city of Twin Falls?" O'Riordan said. "They ignore the elephant in the room, which is the (high nitrate levels) in urban areas."

IDA Executive Director Bob Naerebout said the association is helping fund a joint project with the Idaho Department of Environmental Quality to study the issue further. The industry wants to do its part to address the issue, he said, but it also wants to be treated fairly.

"There are multiple sources of nitrates and all of us ... have an impact," he said. "That's why we're conducting a study. We have to have clean water for our cattle as well as for human consumption."

The study found that unique groundwater flow in parts of Gooding and Jerome counties reduces the effects of nitrate discharges. The area includes a large concentration of dairies and farmland, the report states, but clean water pushing up from the bottom of the aquifer dilutes nitrate levels.

"The effects of nitrate (discharge) are mitigated by clean groundwater coming up," Skinner said. "But the nutrients ... don't just disappear. It just becomes a spring issue instead of a groundwater issue."

Study: http://pubs.usgs.gov/sir/2012/5237/


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