The general sign-up for the Conservation Reserve Program closed last Friday, June 6. If you missed it, or if your field never needed a whole-field contract in the first place, the door that matters is still open: the Farm Service Agency says it will keep taking continuous sign-up offers through July 31 if acres remain under the cap, and continuous CRP is home to the one practice we think every row crop farm with a slope should look at, CP43, prairie strips. The idea fits in a sentence. Put a tenth of a corn and soybean field into strips of native prairie, placed where the water runs, and keep most of the soil and nutrients that would otherwise leave. The claim rests on measurements the STRIPS team at Iowa State University has been taking since 2007.
What the Iowa State trials measured
STRIPS stands for Science-based Trials of Rowcrops Integrated with Prairie Strips. According to the team's research overview, Iowa State scientists and the managers of the Neal Smith National Wildlife Refuge near Prairie City began talking in 2003, and in 2007 they laid out four treatments on twelve small watersheds at the refuge: all row crop, 10 percent prairie at the foot of the slope, 10 percent prairie in contour strips, and 20 percent prairie in strips. The watersheds were 1 to 8 acres with slopes of 6 to 11 percent, farmed no-till in a corn and soybean rotation without cover crops, as Iowa State's summary Small Changes, Big Impacts describes.
From 2007 to 2014, the watersheds with only 10 percent prairie exported 95 percent less sediment, 90 percent less phosphorus and nearly 85 percent less nitrogen in surface runoff than the all-crop watersheds, with 42 percent less runoff water, and on some fields nitrate in groundwater was 70 percent lower. The landowner's guide from Iowa State Extension carries the same figures and adds the line that matters most to a farmer: prairie strips had no effect on crop yield beyond the land taken out of production.
The peer-reviewed version in the 2017 PNAS paper by Lisa Schulte and fourteen co-authors is more careful: catchments with strips lost 20 times less sediment and 4.3 times less phosphorus than the controls, with runoff down 37 percent, while the nitrogen result in surface water carried a wide confidence interval. The biodiversity numbers are firm: 3.5 times the pollinator abundance, 2.1 times the native bird species, 7.8 times the native perennial plant species, and no difference in corn or soybean yield on the cropped ground. In plainer terms, the extension summary counts 51 native plant species inside the strips against 13 in the crop rows, 70 species of native bees, and twice the birds, including grasshopper sparrows, dickcissels and eastern meadowlarks.
Why prairie and not brome
The reason a tenth of a field can hold back nineteen twentieths of the soil is the plant. The team's management overview explains that the cool-season grasses usually sown in buffers, smooth brome and Kentucky bluegrass, are weak-stemmed and lie flat under a driving rain, and the landowner's guide says the same of fescue. Native tallgrass prairie is dominated by stiff-stemmed warm-season grasses such as Indiangrass, big bluestem and little bluestem, with upright wildflowers between them, and those stems stay standing when the water comes. Standing stems slow the flow, and slow water drops its load. Below ground, the guide notes, deep prairie roots build organic matter, improve infiltration and reduce compaction, and a planting of many native grasses and wildflowers offers habitat that exotic grasses or a single-species buffer cannot. This is healing the soil in the most literal sense. It belongs in the same family as the hedgerows and windbreaks we have written about. The pollinator strips are in that family too, with the difference that prairie strips are designed around water first.
Where the strips go
A prairie strip is not a contour buffer of fixed width. The team varies the width by how much water each strip has to intercept, wider where more runs downslope and narrower where less does. The landowner's guide recommends a variable-width prairie area at the foot of the slope, where it filters the water and gives the tractor room to turn, plus narrow strips along the contour as far up the slope as is practical. Places that erode every spring, ground that yields poorly, and land beside a stream or drainage ditch are the first candidates.
The federal practice adds its own rules. The FSA's CP43 fact sheet defines prairie strips as diverse perennial vegetation oriented linearly within row crop fields, 30 to 120 feet wide, covering no more than 25 percent of the cropland in a field. They can run around the field, through it, in terrace channels, beside waterways or in pivot corners, and machinery traffic is allowed where a strip replaces the turn rows on the perimeter. Two cautions from the team's FAQ: sediment settles a few feet into the leading edge of the strip or just upslope of it and may need regrading over the years, and where tile runs under the strip, nitrate can bypass the roots, which is why the team points to saturated buffers as the companion practice. If the field has fresh gullies, deal with those first. Our guide to repairing gully erosion covers the earthwork a strip cannot replace. Our soil erosion repair tips cover it too.
What CP43 pays, and the window this summer
CP43 is a continuous CRP practice, so offers are not ranked against each other. According to the FSA's continuous enrollment page, offers are accepted automatically if the land and the producer are eligible and the program is under its statutory cap, on contracts of 10 to 15 years. The May 2025 fact sheet sets out the money: an annual rental payment based on soil productivity and county cropland rents, factored to a statutory 90 percent limit and capped at $300 an acre; a 20 percent rental rate incentive for water quality practices, the group prairie strips belong to under the CLEAR initiative; a sign-up incentive payment of 32.5 percent of the first full year's rent at contract approval; a practice incentive payment of up to 50 percent for installing the practice; and cost-share of up to 50 percent of eligible establishment costs, with nothing for ongoing management. Land must have been cropped in four of the six years from 2012 to 2017, and you must have owned or operated it for twelve months before offering it.
This year's window has a shape of its own. In its May 12 release, USDA opened general sign-up 64 and continuous sign-up 63 together, both through June 6, with 1.8 million acres available for all CRP enrollment this fiscal year against a statutory cap of 27 million acres; Administrator Bill Beam said the agency was "bumping up against" that cap. Continuous offers are taken first come, first served, and if acreage remains after June 6 the FSA will accept them through July 31, 2025 and consider them in batches. The general sign-up sheet notes that the program is running on the American Relief Act, 2025, which extended CRP authority only through September 30, 2025. Our farm bill primer explains what an extension does and does not settle. Our guide to EQIP and CSP covers the NRCS side.
Seed, site preparation and planting
The landowner's guide asks for grasses and wildflowers in roughly equal shares, from a seed source within 100 miles north or south and 200 miles east or west of the farm, sown at about 40 seeds per square foot; a diverse mix at that density fills the root space below ground and leaves less room for weeds. The FAQ's price range runs from about $100 an acre for the most basic CRP mix, with two forb species making up under 5 percent of the seed, to under $250 for the many moderate-diversity mixes and over $1,500 for forb-rich mixes with rare species.
Ground coming out of well-managed row crops has a reduced annual weed seed bank, which is the easiest start. Check last year's herbicide labels for carry-over and replant restrictions before you order seed, and kill perennial weeds such as Canada thistle before seeding; weedy ground or old pasture needs several rounds of spring tillage or two herbicide passes first. The guide's timing is the dormant season: broadcast after harvest in the fall or after frost and let the freeze and thaw work the seed in, or drill in spring directly into corn, soybean or cover crop residue no deeper than a quarter inch and hope for a moist three to six weeks. Spring and summer seedings favor the warm-season grasses, but the seed may need pretreatment, which most seed houses do before delivery.
The first three years
Mowing is the job in year one, and the strips will not look like prairie. Native seedlings spend their first season building roots, so the annual weeds that germinate from the seed bank will shade them out unless they are cut. The landowner's guide says to mow three or four times the first year, each time the tallest growth reaches about a foot, with the mower set at six inches; the FAQ puts the trigger at knee height and the cut at four to six inches. Either way, mow before the weeds set seed: the seedlings get their light and the crop next door gets less weed seed.
In year two, mow once or twice at eight inches to suppress whatever weeds remain, and spot-treat patches of perennial weeds. Once the prairie plants are established they are highly competitive, and the guide reports no significant difference in weed cover in cropland beside strips compared with cropland without them. From then on the work is removing the top growth every year or two by mowing, baling, grazing or a controlled burn so thatch does not build up. Avoid fall mowing where you can, because standing stems are winter cover for wildlife. If a tenant farms the field, bring them in before the design is drawn: their equipment decides the strip widths, and they need to know whether maintenance is theirs, so the strips are not tilled through or sprayed by accident. That conversation is where managing holistically starts.
What it costs
The landowner's guide puts establishment at about $300 an acre of prairie, and Iowa State's cost sheet, in 2017 dollars, itemizes it: site preparation, a seed mix at about $250 an acre, drilling and packing. The number that matters is the annual one. Annualized over a 15-year contract, a prairie acre costs $353 a year on high-quality Iowa ground, $319 on medium and $279 on low, and because one acre of prairie treats the runoff from about nine acres of crop, that works out to $35, $32 and $28 per protected crop acre per year. Land rent is the bulk of it: opportunity cost makes up 75 percent or more of the total, management 10 to 15 percent, and site preparation and seeding under 10 percent. Under a 15-year CRP contract the team estimates the farmer's cost falls by about 75 percent, to roughly $8 per treated acre per year.
Set that against what the strip saves. The extension summary gives an average all-crop field in the trials losing 4 tons of soil, 35 pounds of nitrogen and 7 pounds of phosphorus per acre a year. Keeping most of that on the field is the first step toward cutting the nitrogen bill rather than replacing what washed away. The strips pay off on the timescale the soil was built on.
Beyond Iowa, and where to see one this month
Prairie strips were designed on Iowa slopes and tested on no-till corn and soybean ground, and the team says so. The PNAS authors estimate that the practice suits about 40 percent of Iowa's row crop land on slope criteria alone, and by 2024, according to the STRIPS site, farmers and landowners were farming with strips in fifteen states, including Minnesota, Missouri, Nebraska, the Dakotas, Wisconsin, Illinois, Indiana, Ohio and Michigan. The University of Nebraska, whose faculty have worked on the trials, frames the decision the way a farm would: find the acres that lose money in most years and compare what a strip costs there with what it returns. Outside the tallgrass region the same logic applies with a local seed list: stiff native stems across the flow path, sized to the water.
Seeing a strip is better than reading about one. Four Iowa State research farms, at Lewis, Chariton, Greenfield and Crawfordsville, host strips and are open during business hours, and the original plots at Neal Smith can be visited after checking in at the refuge's Prairie Learning Center. This Thursday, June 12, Iowa Learning Farms holds a free wetland and prairie field day near Haverhill with the Iowa DNR's private lands biologist on prairie management and the county NRCS conservationist on cost share, and a prairie and pollinator field day follows near Kellogg on June 24. For seed dealers and prairie contractors, see our service providers directory. For the habitat groups that fund native seedings, see our organizations directory.
A list for this summer
- Walk the field after the next hard rain and mark where the water runs and where the soil ends up. That map is the design.
- Pick the foot-slope area and the contour lines, and measure them against the widest implement that works the field. Involve the tenant now.
- Call the FSA office this week about a CP43 offer before July 31, and ask the NRCS planner to lay out the strips within the 30 to 120 foot and 25 percent rules.
- Order a local-ecotype mix of grasses and forbs at 40 seeds per square foot for a fall or dormant seeding, and check last year's herbicide labels first.
- Put four mowings on next year's calendar and a spot-spraying pass on the year after. Then leave the strips alone to become what they are.
A tenth of the field is a small thing to give up. What the trials show is that the tenth, put in the right place and planted with the right plants, holds the other nine tenths together.