For a number of years, there’s been a “dead zone” in the Gulf of Mexico that is caused by nitrogen runoff flowing from farms down the Mississippi River into the Gulf.
But nutrient-runoff problems aren’t limited to the Mississippi River. For more than 40 years, the U.S. EPA has been working with Ohio no-tillers about concerns with Lake Erie phosphorus levels.
So it’s surprising to hear scientists are knocking no-till as a major cause of the Lake Erie concerns. This follows a 2011 algae bloom of more than 2,000 square miles in the lake due to May rainstorms that brought 20% more rain than normal, along with higher-than-normal water temperatures and calm winds that promoted summer algae growth.
A study by researchers at the University of Michigan and eight other institutions places the blame on weather conditions and changing agricultural practices, including no-till.
While no-till reduces erosion, these scientists argue that it leaves high levels of phosphorus-bearing fertilizer in the upper soil, making it more likely to be washed down rivers and into Lake Erie. Other runoff concerns include fall applications and broadcasting fertilizer. Yet the study failed to look at non-ag situations that add to phosphorus levels in Lake Erie, such as the Detroit wastewater plant, the Thames River in Canada and phosphorus in the lake’s sediment.
Spread The Blame
Steve Davis, a Natural Resources Conservation Service watershed specialist at Columbus, Ohio, questions whether no-till is as big a problem as the study implies. “We know agricultural runoff is a huge contributing factor,” he says. “But the question in the scientific community is what percent each of the different management practices on the farms contribute.”
Davis wrapped up a 5-year study in 2011 of the watershed and found the percentage of fields continually planted with no-till was still small.
Pete Richards, a senior research scientist at the National Center for Water Quality Research at Heidelberg University who participated in the study, says no-till’s impact is hard to measure.
“I think the role of no-till is mostly indirect, in that it tends to be accompanied by broadcast application of fertilizer onto the surface without incorporation, which leaves the fertilizer vulnerable to wash-off in successive rainfall events,” he says. “If we could get that fertilizer into the soil, we’d be a lot better off.”
Many farmers do not use true no-till and proponents of the system argue that the advantages of increased infiltration, reduced nutrient losses and improved soil health are not achieved with rotational no-till. “This is obviously a pretty complicated business, and there is definitely not a unanimous opinion about the benefits or disadvantages of no-till,” says Richards.