Making extended crop rotations work

Slideshow: ISU and conservation groups study the benefits and economics of extending crop rotations.

By Jason Johnson

For the past several years the USDA Natural Resources Conservation Service has promoted the adoption of soil health conservation activities. These principles include keeping the soil covered, minimizing soil disturbance, growing plants throughout the year, diversifying with extended crop rotations and incorporating livestock in the cropping system.

Adding a third or more crop to a rotation to increase plant diversity has been the most difficult principle for most Iowa farmers to adopt. There are many reasons for this, not least of which is finding markets for small grains or other potential crops.

For decades Iowa farmers included alfalfa, oats, wheat and other small grains in their corn and soybean rotation. By growing a variety of plant species, past generations more sustainably managed their soils. Extended crop rotations help increase nutrient cycling; better manage weeds, disease and insects; reduce erosion; improve infiltration; and allow more biological activity in the soil.

Can extended crop rotations make a comeback?
An ongoing cropping system research study by Iowa State University indicates that, with the right management, three- and four-year rotations can be just as profitable as traditional corn-soybean rotations.

Led by Matt Liebman, a professor in Iowa State University’s agronomy department, the study compares a two-year corn-soybean rotation, a three-year corn-soybean-oat plus red clover rotation, and a four-year corn-soybean-oat plus alfalfa-alfalfa rotation. Eight years of findings indicate that diversifying the cropping system and integrating livestock consistently boosts productivity, profitability and environmental health.

The ISU research points to the following important observations:

Equivalent profits. Annual net returns did not differ statistically among the cropping systems. Numerically, the four-year rotation returned $413 per acre, the three-year rotation returned $409 per acre, and the two-year rotation returned $384 per acre.

• Better yields. Corn yields improved 3% in a three-year rotation and 4% in a four-year rotation compared to a standard corn-soybean rotation. Soybean yields improved 13% in a three-year rotation and about 17% in a four-year rotation.

• Improved soil health. Soils in extended rotations tested higher for organic matter and microbial biomass and provide the crops higher amounts of usable nitrogen.

• Reduced erosion potential. In a four-year rotation, estimated sheet and rill erosion fell about 35% compared to the corn-soybean rotation. In a three-year rotation, sheet and rill erosion fell about 21% compared to a corn-soybean rotation.

• Reduced herbicide and N fertilizer use. The three- and four-year rotations used 88% and 92% less nitrogen fertilizer and 96% and 97% less herbicide. Corn and soybeans in the three- and four-year rotations received band applications of postemergence herbicides and interrow cultivation. Conventional weed management practices are compatible with extended rotations if careful attention is paid to potential problems with herbicide carryover.

• Reduced disease susceptibility. The three- and four-year rotations exhibited reductions in the incidence and severity of soybean sudden death syndrome.

Liebman agrees that the lack of steady, readily available markets for any crops besides corn or soybeans impedes the adoption of extended rotations. “I also think the decline of mixed crop-livestock farming and a perceived lack of support of alternative crops by agricultural retailers are factors,” he says.

Focusing on finding markets
Groups like Practical Farmers of Iowa are working with farmers and ag businesses to improve the small-grain supply chain. Alisha Bower, strategic initiatives manager with PFI, says many current farmers remember their grandparents growing small grains, but they have never grown them themselves. “We do our best to help farmers ‘relearn’ the skills needed to manage a small grain crop,” she says.

Bower says PFI offers specialized small-grain conferences, monthly educational conference calls, and videos featuring advice from other farmers. “We also offer cost share to help defray some of the risks as farmers go through the first years of honing management and establishing their market,” she adds.

PFI received a $1 million Conservation Innovation Grant (CIG) from NRCS, beginning in 2019, to help revive feed and seed markets for growing small grains in Corn Belt states. “We will work with animal protein companies to conduct small-grains feeding trials and feasibility studies in their supply chain,” Bower says, “as a proof of concept and a method of collecting economic outcomes to include small grains in animal rotations.”

Growing grains for cover crop seed
Small grains for cover crop seed is another market opportunity for growers wanting to extend their rotations. “We can help connect farmers who want to start these businesses with resources on how to do it within the confines of seed laws,” she says. “And we can help them connect with other farmers seeking cover crop seed and seeding services.”

Finding a market for small grains continues to be a primary barrier for farmers, Bower notes. “We engage in a number of projects to help develop markets for these crops,” she says. “We collect production data from farmers who participate in the cost-share program.”

She mentions the Fieldprint Calculator, Cool Farm Tool and the NRCS Resource Stewardship Evaluation Tool (RSET) as tools to help document the environmental impacts of extended rotation systems. “These are valuable tools for companies who have made commitments to reduce the footprints of their supply chains,” she says.

Cost-share assistance available
PFI is seeing high demand for its cost-share program. It is offering $25 per acre on up to 100 acres for diversifying a corn-soybean rotation with a year of small grains and a summer cover crop.

“With low market prices for corn and soybeans, farmers are eager for alternatives,” Bower says. “Farmers are looking at lower input crops, like hay and small grains, to lower their production expenses in this tight farm economy.”

NRCS can also provide planning and financial assistance for conservation crop rotations. In fiscal year 2019, NRCS is offering payment rates of $9 to $11 per acre for up to three consecutive years to extend the crop rotation with small grains. For more information on extended crop rotations, visit NRCS at your local USDA Service Center.

Johnson is a public affairs specialist with NRCS based in Des Moines.

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