FIELD DAY attendees, on a tour of Hamilton County water quality practices, listen to Stratford-area farmer Jim McKee, as he discusses the nutrient intercept wetland, in background, that was installed on his land eight years ago. The wetland is designed to capture nitrogen- and phosphorus-ladened runoff from his fields. The nitrogen is converted into nitrogen gas, released harmlessly into the air. A sediment pond allows the phosphorus, attached to soil particles, to settle out of the water before it flows downstream along an unnamed tributary to Squaw Creek.

By LARRY KERSHNER

“mailto:kersh@farm-news.com”>kersh@farm-news.com

STRATFORD – Cover crops, prairie buffers and wetlands are in-field and edge-of-field land practices designed to hold nitrogen and phosphorus out of surface waters.

Sometimes deciding on which practice should be used is often a hit-or-miss proposition.

But that is changing.

JIM JOHNSON, points out Saturday different features of his soil conservation and water quality practices he installed on his Hamilton County farm near Stratford.

A pair of Hamilton County farmers – Jim Johnson and Jim McKee – hosted a field day Saturday, offering a glimpse at the kinds of practices they employ to keep nutrient-ladened runoff from reaching nearby Squaw Creek.

The event was organized by the Squaw Creek Watershed Authority, which has developed a 20-year plan for improving water quality that flows down Squaw Creek – which flows through Hamilton, Boone and Story counties – and empties into the Raccoon River, from which Des Moines takes some of its drinking water.

For years, water quality efforts on different farms have been tried, with varied levels of success.

However, on Saturday, those attending the event at Johnson’s farm learned of a new matrix formula designed to pinpoint the most efficient practice in any part of a farm, along a waterway, based on terrain characteristics, farming practice and soil type.

Mark Tomer, a soil scientist from the USDA-Agricultural Research Service, introduce the group to the Agricultural Conservation Planning Framework, a GIS-based toolset for precision conservation planning in watersheds.

JAMIE BENNING, gesturing, introduces Hamilton County Jim McKee, facing listeners. McKee told Saturday’s field day participants about his experiment with using oats as a cover crop on a field that will be corn next season.

Tomer said ACPF pinpoints which practices will be most effective in reducing N and P in tile and surface runoff and is capable of mapping those methods, changing the recommendations downstream as soil types, terrain and field practices change.

Tomer said any approach to watershed planning has to consider four needs. They are:

• Recognize uniqueness of each watershed. No two are alike.

• Recognize independence of individual farmers, including them as partners in the process.

• Include a mix of practices – in-field and edge-of-field – to meet Iowa Nutrient Reduction Strategy goals.

• Protect and improve soil resources, increase crop productivity and moderate hydrologic responses to extreme events.

“There is no silver bullet out there,” Tomer said about water quality practices for Iowa meeting nutrient reduction goals. “All plans must be adaptable to each watershed and for each farmer on it.”

He said in any nutrient reduction plan, “soil health is the first line of defense.”

That means soils that are dense with organic material, with deep water-holding capabilities, will stay in place longer in heavy rain events.

Healthy soil, he said, “has minimum leaching, less runoff, is easier to maintain and requires less money in the long run.”

The ACPF is designed to reveal the best practices for controlling, trapping and treating nutrient-loaded tile and surface waters.

These include contour filter strips, grassed waterways, water sediment control basins and conservation cover crops.

A nutrient intercept wetland, Tomer said, is one practice that captures and treats N- and P-rich tile and surface water within the stream bed, without backing water up in fields.

Tomer demonstrated how the ACPF maps out each segment of stream tributaries, breaking them up in segments about two-tenths of a mile, and recommends how best to preserve the waterway and water quality.

For instance, one segment may recommend streambed stabilization only, while a little downstream stabilization and deep-rooted vegetation is recommended.

A little farther, the matrix would recommend planting stiff-stemmed grasses and a multi-species buffer zone, without streambed stabilization.

Tomer said the ACPF will lead to more accurate measures, spending funds where they are likely to be more effective, rather than guessing which practices would work best in any given place.

A lot of work

Host farmers Jim and Anita Johnson said installing his conservation measures “is a lot of work, but you have to start correctly.”

Jim Johnson said they bought the farm 25 years ago, but started managing the acres themselves six years ago.

They filled in three eroded ravines, Jim Johnson said, built berms to direct runoff water into an existing pond.

They planted flowering prairie mix throughout the 17-CRP acres, and planted big blue stem and Indian grass for wildlife habitat in the ridges above.

He said the Hamilton County office of the Natural Resources and Conservation Service assisted with his designs.

“They said we had to mow it (CRP acres) four times the first year,” Johnson said. “It was hard to mow down those flowers, but I mowed it four times faithfully.”

The mowing encouraged thicker growth, creating a natural barrier to weeds, Johnson said.

Jim McKee also conducted tours of his cover crops and his nutrient intercept wetland.

At the wetland, he explained tile water and field runoff flow into the device, which is right in the streambed of an unnamed tributary of the Squaw Creek.

Natural forces denitrify the N while the water is being held up, and a sediment pond settles out P-ladened soil particles before the water continues downstream.

A set of water monitors automatically collect samples of water flowing into and out of the structure to assess its effectiveness.