Focus On Phosphorus

These tips can reduce the load in sensitive watersheds.

Strip-till demonstrations, such as this one in the Upper Macoupin Creek Watershed, help farmers understand the strategy behind improving phosphorus management, Image by Illinois Soybean Association

Phosphorus management requires a balancing act between maximizing yield potential and minimizing environmental risk for farmers in sensitive watersheds.

The Upper Macoupin Creek Watershed, in southwestern Illinois, is one of those critical areas where balance is being sought. The 617,000-acre watershed loses more than 2 pounds of phosphorus per acre per year.

“The watershed is one of the three highest phosphorus-yielding watersheds in the state, with much of the loss attributed to nonpoint sources like agriculture,” says Kris Reynolds, American Farmland Trust natural resource conservationist. “Soil types, topography, tillage practices and erosion rates influence the amount of phosphorus that leave a watershed.”

Reducing phosphorus loss in the watershed is key to meeting goals of the Illinois Nutrient Loss Reduction Strategy (NLRS). The NLRS is a statewide effort with the short-term goal of cutting nitrogen losses from fields by 15% and phosphorus losses by 25% by the year 2025. The Soil Health Partnership (a National Corn Growers Association initiative), along with the Illinois Soybean Association, American Farmland Trust and others, are working with farmer-cooperators to identify the best strategies.

Taking Steps. So far, reduced tillage and cover crops offer promising solutions. James Hoorman, Natural Resources Conservation Service (NRCS) Northeast soil health specialist, says reduced tillage and cover crops act as natural buffers, helping to build back soil organic matter, tie up nutrients for later release, improve water infiltration and provide a host of other benefits.

Bill Heyen, Heyen Farm, Gillespie, Illinois, is one of the farmer-cooperators. His family raises corn and soybeans on more than 2,500 acres in the Upper Macoupin Watershed.

“I was optimistic about strip-till results heading into harvest. The crops looked good, so this may be a way for me to reduce phosphorus loss,” he says. “I am willing to continue with strip-till and planting cover crops, as long as it makes economic and conservation sense.”

To succeed with cover crops, Scott Wohltman, La Crosse Seed, Wheeler Illinois, recommends starting with a small acreage to make sure they make sense for a particular farm. “A common first choice is cereal rye. It can be planted later in the fall for flexibility to follow corn or soybean harvest,” he says. “Legumes and brassicas often need six to 10 weeks prior to first frost, so they must be planted earlier than rye.”

Build A Base. To manage phosphorus with cover crops, Wohltman suggests planting a grass as a base. “Preventing wind and water erosion is one way to slow phosphorus losses. An annual ryegrass or cereal grain with a brassica and/or legume is a good solution. Many brassicas sequester phosphorus, while the grass will slow any nutrient loss between winter and spring,” he says.

Illinois farmers are taking note of the options. The Illinois NLRS biennial report released last August noted 200,000 acres were dedicated to best-management practices in 2010, which increased to 425,000 acres in 2015 across the state. From 2011 through 2015, cover-crop use increased by 123% on tile-drained cropland and 66% on non-tiled cropland.

While AFT’s Reynolds is optimistic farmers will continue voluntary nutrient-management efforts, any cutback in federal regulations may slow actions. “When the NLRS first came out, there were many people talking about voluntary adoption of conservation practices to stave off potential future regulations,” he says. “I do not hear as many of those conversations today.”