Testing farm soil can help in algae fight

[USA] Ohio’s ongoing problems with toxic algae likely won’t be solved anytime soon, scientists say. They didn’t start overnight, and they won’t be turned around overnight, either.

But some practices already in place could help slow the flow of fertilizer from farm fields to waterways that feeds the algae that plague Lake Erie and other Ohio lakes. In some cases, it’s just a matter of getting farmers on board.

One such practice is soil testing Brisbane, in which soil from a farmer’s field is tested for potassium, acidity and phosphorus.

Phosphorus, a key food for plants, also is a key food for algae. Scientists have recommended cutting the amount of phosphorus in the watershed that feeds western Lake Erie by 40 percent to reduce algae blooms.

As many as 80 percent of farmers already test their soil, said Greg LaBarge, an agronomic-systems field specialist for the Ohio State University Extension. The tests can be expensive, however, which keeps some farmers on the sideline.

Here’s why testing is important: Crops such as corn, soybeans and wheat need only so much phosphorus. Whatever they don’t absorb stays in the ground, where it can be washed out by rainstorms into streams and rivers that feed Ohio’s lakes.

Soil tests show how much phosphorus already is in the ground. And scientists know how much phosphorus each plant needs.

“You don’t need to be adding phosphorus where it’s not needed,” said Chris Winslow, interim director at Ohio Sea Grant and Ohio State University’s Stone Laboratory, which study the lake.

“And we have the technology in tractors where, if you actually knew what your soil type was as it was driving over your field, it can actually adjust the amount of fertilizer it’s putting on your field.”

That means farmers would spread only the phosphorus needed, meaning less would end up in the watersheds.

Libby Dayton, a soil scientist at Ohio State University, has been studying soil samples for years.

Scientists in her lab study runoff samples from 30 farms across Ohio, hoping to get answers for farmers about how their farming practices affect the environment.

Dayton said the data show that the amount of phosphorus in Ohio’s farm fields is decreasing.

“I think you’ll also find that fertilizer sales data shows that fertilizer sales are trending down,” she said. “I think that demonstrates that the farmers are getting the message loud and clear — they are changing their practices.

“But it takes a lot of years to change the soil.”

Jason Greve, an agronomist and farmer who grows corn, soybeans, alfalfa and wheat in Shelby County, said he tests every half-acre of soil every three or four years.

Doing that, he said, saves money on fertilizer.

“Growers want to do everything they can to reduce that expense as much as possible,” Greve said. “And we also want to be good stewards.

“If we can make these applications and know that we are 100 percent correct as far as placing these nutrients exactly where they need to be, hopefully we’re doing our part to help eliminate some of the environmental issues that are going on within Ohio.”


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