North central Iowa worst in N, P pollution
FORT DODGE – According to John Holmes, and Iowa State University Extension crops field specialist, an agriculture engineer graduate who earns his degrees in 2013 could spend his entire career to helping Iowa reach its 45 percent nutrient reduction goal and be at retirement age before the state reaches that goal.
Holmes was talking to a handful of farmers and agronomists on March 5, in Fort Dodge, discussing the results of two years research on the best farming practices needed for Iowa ag reducing nitrogen loss into surface waters by 41 percent and phosphorus losses by 29 percent.
He said the 45 percent statewide goal for reducing nitrogen loss into surface waters could take as long as 30 to 40 years.
“It’s going to be a process that the community of farmers and cities to get on board,” Holmes said. “We need to apply the science,” with cooperation from farmers, agribusinesses county officials and farm organizations.
In 2008, Iowa was identified by the Gulf Hypoxia Task Force, chaired by the Environmental Protection Agency, as one of three states contributing the most nitrogen and phosphorus into the Upper Mississippi River Valley, creating the algae blooms in the Gulf of Mexico.
The area is referred to as the dead zone because algea absorbs the water’s oxygen, making it impossible for fish and other wildlife to exist.
As a result, Iowa farmers were assigned the task of reducing N and P loads in surface waters by 41 and 29 percent.
There is no time limit, but the EPA said measurable improvements must be measurable promptly.
North Central Iowa – comprising the bulk of the Boone River and Des Moines River watersheds – was identified as the the state’s hot spot for N and P losses.
After two years of study by ISU, U.S. Department of Agriculture, Iowa Department of Agriculture and Land Stewardship, and Natural Resources Conservation Service have targeted several land management practices that will help meet that reduction goal, but it will come with a price, Holmes said.
Basically, nitrogen needs to be stopped before it leaves the tile, Holmes said, and phosphorus halted by stopping water erosion.
The two-year study indicated a number of ways farmers can better manage and preserve soils, keeping N and P in the fields. These would include (assuming the entire state practiced them):
All fertilizer applied in the spring: 6 percent N reduction.
Using only liquid hog manure: 4 percent reduction
Planting cover crops in fall: 30 percent N reduction.
Growing crops with extended rotations: between 30 to 54 percent depending on how many crops in rotation.
Re-establishing wetlands: 52 percent N reduction.
Installing bioreactors between fields and tile discharge points: 43 percent N reduction.
Taking 6.5 million Iowa acres out of row crop production (back to 1987 levels) and returning it to pasture: 18 percent N reduction.
Planting buffer strips: 91 percent P reduction.
The research shows the goals can be met, however, most come with a cost, a couple save money, and all, according to Dr. John Lawrence, an ISU ag economist, benefits cleaner local surface water, as well as reducing N and P loads downstream.
One land management scenario that would meet Iowa farmers’ nutrient reduction goal included fertilizer application only to the point of reaching maximum return on total nitrogen (MRTN), plus 60 percent of acres get cover crops, plus 27 percent of the land treated with wetlands and 60 percent of tiled fields have bioreactors, would cost statewide $3.22 billion.
A second scenario would have Iowa farmers fertilizing at the MRTN rate, use inhibitors on all fall-applied nitrogen, side-dressing all spring-applied nitrogen, 85 percent of all tiled fields with bioreactors, 85 percent of applicable land with controlled drainage and 38.25 percent ag land treated with a wetlands, would cost $4.81 billion.
A third scenario would have Iowa farmers fertilizing at the MRTN rate, use inhibitors on all fall-applied nitrogen, side-dressing all spring-applied nitrogen, 70 percent of all tiled fields with bioreactors, 70 percent of applicable land with controlled drainage, 31.5 percent ag land treated with a wetlands and 70 percent of all ag streams with buffers, would cost $4.04 billion.
The EPA said it will be working with federal and state authorities to stimulate cost-share programs to encourage farmers’ transition to better land management with reduction of N and P in mind.
Since north central Iowa is identified with the largest N and P loss rates in the state, Holmes said, farm in that region would likely be front in line for any future federal and state assistance programs to adopt measures.
“Cover crops will be the biggest first step,” Holmes said, “but expect a push for wetlands, too.”
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