To the relief of southern Idaho farmers and ranchers, the state Division of Environmental Quality has reported that 96 percent of the rural wells tested for nitrates met government standards for drinking water.

"Obviously, we are pleased the vast majority of the wells tested are within drinking standards," said Jim Yost, an Idaho Farm Bureau spokesman. "But we are equally pleased that this pilot program brought together so many agencies in a successful testing effort."In recent weeks, the Farm Bureau collected water samples from more than 250 private wells in south-central Idaho. They were tested for nitrate concentrations at the University of Idaho.

The Division of Environmental Quality then analyzed the results in what was described by one official as the largest canvassing of private wells ever in Idaho.

Nitrate concentrations that exceeded 10 milligrams per liter of water are considered unsafe by state and federal agencies. Drinking water with high levels of nitrates is hazardous primarily to infants and often is an indicator of contamination by other more dangerous chemicals.

Most of the 14 wells exceeding safe-water guidelines were between 10 and 20 milligrams nitrate per liter. The highest nitrate concentration found in any well was 26 milligrams of nitrate per liter, officials said.

The wells with high nitrate levels will be studied to determine the cause of the nitrate contamination and will also be tested for pesticide residues, Yost said. Those wells were also tested for harmful bacteria, which three were found to contain.

"We will be examining depth of wells, well casings, ag practices, septic systems and other factors that might be causing the elevated levels," Yost said.

Nitrates are essential for most plants and occur naturally, but fertilizers, animal and human waste, compost and sewage can leach excessive amounts into groundwater.