We know that runoff is going to happen. Thanks to weather, it’s one component that can’t be controlled.
“But what you definitely can control is what’s in that runoff,” says Amber Radatz.
The co-director of University of Wisconsin Extension’s Discovery Farms shared three keys to controlling nutrient loss on your farm at the Discovery Farms conference held last month.
1. Control Soil Loss
Radatz says on-farm data taken by Discovery Farms shows the more soil you lose, the more phosphorus (P) you lose. About 1 pound of P is lost with every 1,000 pounds of soil.
Soil loss occurs the most from April through June, Radatz says.
“That is the time you should think about protecting the soil,” she explains. “If you’re discouraged by your wimpy cover-crop growth in the fall, remember it’s really not for fall protection, it’s more for spring.”
During those spring months, no-tillers should scout their fields and investigate where water flows. Look for areas where there’s sedimentation in field corners or soil covering small seedlings — signs of in-field movement, Radatz says.
If you’re already using no-till in those areas, then consider adding waterways or dams to keep soil from moving.
2. Watch Application Timing
Discovery Farms’ research shows that when soil is frozen, particulate runoff doesn’t occur because there’s no soil movement. But they can still see a loss in dissolved P.
Where is the P coming from? Radatz says it’s when applications are made right before a runoff event.
“Most of the P loss was coming in one month of the year when snow was melting,” she explains.
By better timing the applications, she says, growers can reduce those losses by 2-4 times.
Wisconsin no-tillers can refer to the Runoff Risk Advisory Forecast, a map that shows when the risk of runoff is moderate or high in specific areas, to avoid making applications before a runoff event.
3. Consider Nutrient Placement
Discovery Farms looked at P loss on several farms in Vernon County in Wisconsin. Two of the farms were no-tilled and another incorporated manure. The disturbance caused by the incorporation was similar to a chisel plow, Radatz says.
Their data showed that the farmer using manure incorporation was able to keep his dissolved P losses very low, the lowest of all the farms. But when they looked at total P loss, which includes particulate P, it was a different story.
There wasn’t much difference in total P loss compared to dissolved P loss for the no-tillers, but the farmer doing incorporation saw a very high amount of total P lost one year because he lost a lot of soil.
“Three out of 4 years he had low dissolved P numbers, but in that last year he doubles everybody in P losses, not to mention losing 4,000 pounds of sediment per acre,” Radatz says. “I think manure incorporation is great, as long as we can balance it without losing so much soil that we’re just shooting ourselves in the foot.”
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