MINNEAPOLIS (AP) - The Minnesota Department of Agriculture plans to test 70,000 private wells in the state's farming regions to measure nitrogen contamination that seeps into the ground from fertilizers. The state says the level of pollution from tons of fertilizer that's applied each year across the southern two-thirds of the state is rising. A survey in 2011 found excessive pollution in 62 percent of the wells monitored by the state in central Minnesota, where the groundwater is most susceptible. Besides the well testing, the Star Tribune reported Friday (http://strib.mn/17xcUMU ), the state hopes to persuade farmers to better control their use of fertilizer. That could include asking them not to fertilize in the fall when the risk to groundwater is greatest, or inching toward mandatory steps such as requiring them to plant different crops or take land out of production. Environmentalists don't think the plan is strong enough because it assumes landowners will act voluntarily. Minnesota farmers have taken steps over the years to minimize nitrogen losses and reduce unnecessary fertilizer applications. As a result, nitrogen use per bushel of corn has dropped sharply. Still, the number of acres devoted to corn has risen, and so have fertilizer sales. Drinking water contamination has also risen. The new plan would start with well testing in areas known to have groundwater problems. If they find that 5 to 7 percent of the wells in an area are contaminated, officials would create a local advisory group, including farmers, to recommend better practices. But Randy Ellingboe, a manager at the Minnesota Department of Health, said waiting until wells show nitrates at 7 parts per million might not give communities and homeowners enough time to avoid expensive treatments. And Kris Sigford, water quality manager for the Minnesota Center for Environmental Advocacy, a nonprofit environmental law firm, said the new plan is weaker than one established in 1990. But agriculture officials say relying on landowners to make the right choices will work. Pilot projects have proved that local communities and farmers "want to be part of the solution," said Greg Buzicky, who headed the development of the Agriculture Department's plan. Buzicky said department officials will consider recommendations for changes to the plan then submit it to Agriculture Commissioner Dave Frederickson for final approval.