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Wheat Helps a No-Till Rotation
Growing winter wheat in rotation with corn and soybeans is uncommon around Pender, Nebraska, but no-till farmer Randy Rink has done it for more than a decade. He added the wheat to jump-start his then-new no-till system. Over time, wheat’s merits have proved themselves, creating rotational diversity and enhancing soil quality.
Rink grows wheat every fifth year, following a four-year sequence of corn-soybeans-corn-soybeans. A multispecies cover crop comes after the winter wheat.
“The rotation provides a three-crop break between corn crops,” says Rink. “The break is long enough to eliminate corn diseases, and, as a result, the corn is healthy.”
Opportunity For Cover Crops
Another key benefit of the winter wheat is that it gives a good chance for a cover crop to get up and going before freezing up. Rink plants the cover crop right after harvesting the winter wheat in mid- to late July.
“Planting a cover crop in midsummer gives time to get enough growth before freezing up to benefit the system,” he says. “If I try to plant a cover crop after corn or soybeans, it’s tough to get enough growth to realize a benefit from the cover crop.”
The multispecies cover includes both warm- and cool-season plants. The cool-season species thrive in the fall.
“The normal freeze date here is October 4, so I get about 60 days of growth on the cover crop,” says Rink. “The crop can get huge. I’ve grazed it, and sometimes the cover ends up being about as tall as the cattle.
The leaves of the brassicas are lush and green, but they die at freeze-up. I just plant straight into the leaf material in the spring.”
The residue from the cover crop contributes organic matter to the soil system, and the growth and decomposition of the plants recycle nutrients.
“The legumes in the cover crop fix nitrogen, while the crop, as a whole, scavenges excess nitrogen from the soil, keeping it from leaving the system,” he says. “After drawing nitrogen from the soil, the cover crop puts it on the surface in the form of plant material. When the plants break down, the nitrogen is still there.”
In its vegetative state, the cover crop creates a moist environment at the soil surface. This setting promotes the microbial activity needed to break down the wheat straw.
“Because I harvest the wheat with a stripper head, the stubble stands 25 to 30 inches tall after combining,” says Rink. “When I no-till plant the cover crop, I knock down some of the straw. Afterward, it’s like a blanket covering the ground. The straw has a lot of lignin and a lot of carbon.”
As corn grows in the field the following season, the decomposing cover of straw prevents water from running off the soil surface. It also prevents soil erosion.
The root structure of wheat further reduces the chance for erosion. “Wheat has a fibrous root system that serves to tie the plants together and to anchor the soil,” says Rink. “With row crops, some areas of soil don’t have roots, and because of that, soil can wash from these places.”
Yet another benefit of winter wheat in Rink’s rotation is that it provides open fields where manure can be spread. Rink purchases manure from commercial feedlots nearby and applies the manure to fields after winter wheat is harvested.
Of the 2,000 acres in his rotation, he annually applies manure to the 400 acres where wheat was previously grown.
“The feedlots are always looking for places to send manure in midsummer, and the wheat fields work well because they’re harvested by that time,” says Rink.
He has applied the manure in a couple of ways. “Often, I’ve stockpiled manure on harvested wheat fields and let it compost,” he says. “I’d let the cover crop grow up, and then I’d spread manure in late fall.”
Rink engaged a custom applicator to apply manure to harvested wheat fields before the cover crop was planted. The manure was applied at a variable rate according to the results of a grid survey compiled from soil sampling.
“I previously applied the manure at a rate of 20 tons per acre,” he says. But now he has the ability to apply it at a variable rate of 10, 20, or 30 tons per acre.
Rink applies no commercial phosphorus because the manure provides enough phosphorus for five years of crop production. He does apply nitrogen, however, to cash crops.
“The manure provides nitrogen for the corn crop, which allows me to reduce my nitrogen inputs,” he says.
While planting corn following the cover crop and manure treatment, Rink puts down 50 pounds per acre of 10-34-0 starter fertilizer.
“I’m trying to build and improve the soils,” he says. “Overall, the natural fertility of the soil has been getting better, and the organic matter is improving. I’ve been taking off the grain but adding manure and leaving the wheat, corn, and soybean residue. As a result, I have very little runoff and few gullies.”
Better Soil Balance
Analyses of soil carbon-to-nitrogen (C-to-N) ratios show that Randy Rink’s soils are in balance. “A C-to-N ratio of 10-12 to 1 is ideal, and my soils are at that level,” he says. “When soil is balanced in C and N, the soil microbes can really go to work and recycle residue.”
With wheat adding large amounts of C and the legumes and other sources contributing the N needed to break down the C, soil life is abundant. This fosters rapid breakdown of residue.
“In my system, I’m recycling all the plant material,” says Rink. “Including one year of wheat in the rotation has done me a lot of good.”