Relay cropping proves its worth
Relay cropping soybeans and cereal rye potentially doubles net profit per acre over monocrop soybeans and improves soil structure to boot, according to on-farm trial results in northeastern Iowa. The three-year trials were part of the Multi-Cropping Iowa initiative launched in 2019 by a partnership between the:
• Northeast Iowa Resource Conservation and Development (NIRCD)
• Iowa Soybean Association
• Iowa Department of Agriculture and Land Stewardship
• USDA Natural Resources Conservation Service
“Almost all of the participating farmers already practiced no-till,” says Ross Evelsizer, NIRCD natural resources project director. “Some had already been relay cropping for several years. Others grew monocrop soybeans in a corn-and-bean rotation. Some grew cover crops and some did not.”
The trials also included a conventionally tilled field growing a rotation of corn and soybeans without cover crops. Small grains were included in rotations to permit timely fall-planting of cereal rye.
Twice the Net Profit
Relay cropping is a version of multi-cropping where the second crop is planted into the first crop before harvest. In the relay-cropped fields in the Iowa trials, farmers planted cereal rye in early to mid-fall after harvesting a small grains crop or corn for silage. They planted soybeans into the rye stand in April, when the rye was about 10 inches tall. They harvested the rye for grain in mid- to late July.
“Once that rye is harvested, the beans really take off and can be harvested when mature, typically in October,” says Evelsizer.
“With the relay cropping, we saw a yield drag on the soybeans averaging 13 bushels per acre,” he says. “But the average yield on the rye is 30 bushels per acre. We typically harvest 70 bushels per acre between the two crops.
“The average per-acre net profit was $50.90 more for relay cropping than for monocrop soybeans,” adds Evelsizer. “That’s about twice as much net profit per acre for relay cropping than for the monocrop soybeans.”
Reduced input costs for herbicide also favored greater profitability for the relay-cropping system.
Soil tests taken at the start and completion of the trial period showed little differences in soil organic matter in samples taken from no-till relay-cropped fields and no-till fields growing cover crops.
Aggregate stability, however, was highest in the relay-cropped fields—higher even than in no-till cover crop fields.
One reason for this, Evelsizer believes, is the longer period of time living roots are in the soil in the relay-cropping system and the greater root density produced by the maturing cereal rye.
The importance of enhanced aggregate stability is its benefit to surface water management. “Having large acreages managed by relay cropping could have beneficial impacts on watersheds,” says Evelsizer. “Cover crops and no-till do that, too, but relay cropping is a really good way to do that. The benefits can be produced faster.”
Choosing a longer-season soybean variety is important in a relay-cropping system where soybeans are planted in April into cereal rye that will be harvested for grain.
“Producers in our Iowa field trials planted a maturity group 3.5 soybean rather than a maturity group 2.5 variety, for example,” says Ross Evelsizer, Northeast Iowa Resource Conservation and Development natural resources project director. “That keeps the bean from bushing out too quickly. Once the rye is harvested, the beans take off.”
Planting soybeans in 30-inch rows with two rows of rye in between was a common practice for producers in the field trials. “However, one producer planted both crops together and had great results,” says Evelsizer.
When the cereal rye is ready to harvest, it stands above the soybeans.
“That’s why producers preferred cereal rye for relay cropping over winter wheat, because wheat doesn’t grow as tall as rye,” he says. “Most trial participants used a standard platform head on the combine to cut the cereal rye. But an adapted row crop head may be more efficient. It’s important not to cut the beans because it does impact their growth if you clip them.”
The sky’s the limit, he notes, when choosing crops for multi-cropping. “You just need to find noncompetitive plants that can grow together without shading each other out,” Evelsizer says.
Why Watersheds Benefit
Watersheds benefit because of the improved water infiltration resulting from the larger pore spaces created in the soil when aggregate stability increases.
“Infiltration tests showed that on the conventional field, the second inch of rain took a couple of minutes to infiltrate,” says Evelsizer.
However, a 4-inch rainfall took two and a half minutes to infiltrate the relay-cropped field, This nearly doubled the conventional field’s infiltration rate.
“When a watershed experiences flooding resulting from a large precipitation event, relay cropping can help reduce the severity of flooding because of its ability to improve soil structure and thus water infiltration,” he adds.
Preliminary trial information also shows potential mitigation of flood risks. “If every acre in a given watershed were converted to relay cropping, that could potentially reduce flooding in that watershed by 50%,” says Evelsizer. “The benefits decrease in a catastrophic flood event.”
In locations where soils tend to waterlog in spring or after heavy rains, the moisture-managing benefits of relay cropping could potentially make it easier for conventional-till farmers to transition to no-till.
While the field trials did not measure weed suppression, anecdotal feedback from farmers indicates that relay cropping suppresses weeds, and some farmers were able to cut herbicide inputs as a result.
“Including cereal rye in the relay-cropping phase is the key; there’s no place for the weeds to grow,” says Evelsizer. “Some producers had replicated strips on their fields where they eliminated fertilizer and herbicide. On some of these strips farmers realized five times higher net profit per acre than on monocrop soybeans because they were able to cut input costs without losing too much yield.”
Soybeans rapidly take off following the harvest of cereal rye.
Beyond its ability to increase profitability by cutting inputs while sustaining yields, relay cropping—or any form of multi-cropping—is a practice offering a potential fit for the emerging carbon marketplace.
“There’s potentially a lot of opportunity there for multi-cropping,” says Evelsizer. “Because there are plants in the ground for a longer period of time, the soil is able to take up much more carbon. At the same time the plants are protecting the soil.”
In his view, this is a cropping system for the future. “We have to make some serious changes in agriculture because we can’t keep losing soil at the rate that we presently are,” he says. We have to do things differently, and multi-cropping is one way to address our challenges.”