SMALL GRAIN UPDATE: Rye for swine and the unintended consequences of cover crops

By CARSON HUGHES carson.hughes@apgsomn.com

Is rye a cost-effective diet for pigs? Do cover crops live up to the hype? What small grain varieties are best suited for southern Minnesota?

Educators with the University of Minnesota Extension Office discussed these questions and more with a crowd of around 20 farmers at the Le Sueur County Fairgrounds in Le Center Tuesday.

Diane DeWitte, a swine educator with the Extension Office, opened the small grain update by diving into recent research on how a rye diet impacts organic hog production. Researchers aimed to see if rye could work as a cost effective replacement for corn and lower the costs of raising livestock.

The results so far have been promising. In 2021, researchers at the U of M Morris developed 17 acres of a hardy, high-yielding hybrid winter rye variety called KWS Tayo. The rye was used both as a source of feed for the swine and as bedding.

With 800,000 seeds planted per acre, the yield averaged 104 bushels to the acre and 1.8 tons of straw per acre.

Researchers then compared pigs on a corn and soybean diet to 100 pigs raised with a half corn, half winter rye diet and found no statistical differences in the growth of the pigs. DeWitte noted that hybrid rye provides 92% of the energy of corn. While not as good as wheat, the rye served as an effective substitute for corn and provided more energy than barley and oats.

The combined savings of using the rye for feed and bedding was estimated at approximately $738 per acre, but DeWitte cautioned that total may be higher than what one would normally expect.

“It seems a little high, and there are some reasons for that. One is that the yield was pretty darn good. Some years, they’ve only had 43 bushels to the acre, and you wouldn’t see that kind of savings if you didn’t have 100 bushels to the acre,” said DeWitte.

At the time of the experiment, corn prices were also approximately $4 more than rye per bushel, contributing to the large cost savings. U of M researchers are continuing with a second trial this year to collect more data.

A second phase of research aims to test pork quality of pigs raised on rye with blind taste-testing trials.

“We’re just halfway through the project,” said DeWitte. “Some of the points to take home would be putting hybrid rye into your crop rotation, it would have to be a substitution for another small grain, but it can have some weed control effects and the long-term yield could be good.”

Cover crops

Across the United States and in Minnesota, an increasing number of farmers have adopted cover crops like oats and rye into their rotations as conservation agencies and advocates have promoted the crops as an important tool for preventing erosion and storing water, reducing nitrate contamination and maintaining soil fertility.

But U of M Small Grain Specialist Jochum Wiersma warned attendees that the productivity benefits of cover crops to farmers aren’t as lucrative as they are often advertised to be.

“The major question really is, are we really losing productivity? Look at the average state yields for corn, we’re still going up — pretty substantially actually. That’s not all genetics, I don’t care what the breeders say,” said Wiersma.

As a nitrate reducing agent, Wiersma suggested cover crops have a limited impact when put into a corn and soybean rotation. Wiersma cited a 2006 study in the

Agronomy Journal showcasing the potential of fall rye to reduce nitrate run-off in Southeastern Minnesota. At its peak, the study found rye planted on Sept. 15 could cut nitrogen loss by 40% on May 30.

But Wiersma said cover crops are often terminated well before their maximum potential in late May and June so that corn can be planted in early May without any vegetative competition to get a higher yield.

“The vegetative growth after soybeans and corn, it doesn’t take up enough nitrogen to make a difference, 15 pounds maybe,” said Wiersma. “The termination of your cover crop too early, before the potential of leaching is the greatest May through June, you are eliminating that cover crop.”

By April 30, the potential nitrate loss attributable to rye is closer to 30% and below 20% if terminated by the end of March, according to the study. That assumes the rye is planted by Sept. 15, but Wiersma noted if the crop is planted too early, it’s susceptible to pests like the Hessian fly and armyworms.

Hessian flies are known to lay their eggs in vegetation in the fall, which then develop into larvae in the summer and feed on grain stems. In recent growing seasons, the pest has increased its presence in Minnesota as the adoption of crops like winter rye and barley have given them places to nest.

Rye can also serve as a host for armyworms and their offspring. Corn planted into a rye cover crop are the most susceptible, but the larvae are known to eat soybeans as well if they are hungry enough, Wiersma noted.

“To me, rye as a means to reduce nitrate leaching is kind of like a band-aid on an arterial bleed, because you are terminating the rye too early to really make a difference,” said Wiersma.

One of the other agricultural benefits of cover crops is their capacity to increase soil infiltration, allowing fields to dry faster after heavy rains and flooding. But Wiersma advised that their utility in managing water is mixed when a growing season with too much moisture can be followed by a drought the next year.

“As a way of managing soil moisture, I think cover crops are a crapshoot because weather is unpredictable,” said Wiersma.

When considering cover crops, Wiersma advised that farmers should evaluate them as any other crop.

“Rather than thinking about cover crops, why don’t we just think of it as a crop and just widen our rotation?” said Wiersma. “If we want to go down this path and make this part of our system, we still have to adhere to all the old principles. We cannot beat Mother Nature, she’s going to beat you if we ignore all those things that we already know.” n

Farming has never been a vocation for individuals looking for easy work. Farmers typically work long hours, braving the elements regardless of how unpleasant the weather may be.