Blair Sawall harvested almost-chest-high brown midrib (BMR) sudangrass in mid-July this year, just more than a month after he planted it.

“We cut it in 33 days and it was over 40” tall,” says Sawall, who milks 150 cows near Clintonville, in east-central Wisconsin.

He’s one of many Upper Midwestern dairy producers who planted the grass as an emergency crop after coming up short on forages because of a dry 2012 and alfalfa winterkill. Sorghum-sudangrass is often considered a better choice. But Sawall took the advice of Dave Robison, Legacy Seeds forage and cover crop manager, who prefers sudangrass.

Sudangrass grows fast, delivering harvestable forage two or three weeks sooner than sorghum-sudangrass, Robison points out. The first-cutting yield usually can’t match that of sorghum-sudan, but season-long production is at least as high.

“If we’re getting two cuttings with sorghum-sudan, typically we’re getting three cuttings with sudangrass,” he says.

Both warm-season grasses thrive in the heat of summer, when cool-season grasses and legumes peter out, Robison says.

But they don’t do well in cool climes, says Dan Undersander. That’s why the University of Wisconsin Extension forage specialist doesn’t recommend either grass for most of his state. He planted BMR sorghum-sudangrass at Marshfield in central Wisconsin in 2011.

“It didn’t get over 18” tall. We didn’t get a ton per acre planted in June,” he reports.

Undersander calls sorghum-sudangrass a “wonderful crop” for Wisconsin counties south of the Minnesota border and for Iowa, Illinois and other states farther south.

“But for us, it depends,” he says. It grows well when the daily high temperature hits 80° or higher, “and we just don’t have a lot of that most years.”

Although sudangrass grows better than sorghum-sudan in cool weather, his southern Wisconsin recommendation holds. BMR sudangrass is generally higher in quality than BMR sorghum-sudan, but maturity at cutting is the most important forage quality factor, says Undersander.

Robison says sudangrass is grown successfully as far north as Minnesota, North Dakota and Michigan’s Thumb Region. But he agrees that it performs more consistently farther south where temperatures are higher and the growing season longer.

For best quality, sudangrass and sorghum-sudangrass should be harvested when they’re 36-40” tall, advises Undersander. BMR hybrids of both crops can deliver dairy-quality forage and almost as much tonnage as conventional varieties. He puts the BMR yield drag at about 5% compared with 15% for BMR corn.

Sudangrass can be grazed or made into silage or hay, but sorghum-sudan has thick stems that dry too slowly for hay in the eastern U.S., Robison says. Sudangrass has a higher leaf-to-stem ratio, too, making it more palatable as a grazing crop. When graziers move cows from a grass-clover mix to BMR sudangrass, they often get a milk production boost, he claims.

Proper fertility and timely harvesting are keys to success with both crops, he adds. Make sure the grasses have sufficient nitrogen, and harvest them at the right combination of yield and quality. It’s also important to leave 6-8” of residual for fastest regrowth, says Robison.

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Legacy sold its entire BMR sudangrass seed supply last spring – two semi loads – along with six or seven loads of conventional sudangrass seed. Robison doubts he’ll ever sell that much seed in Wisconsin again, but expects sales of the BMR variety to increase. He advocates its use in a series of annual forages capable of producing 10 tons of dry matter per acre per year.

The first harvest in the program he proposes is a fall- or spring-planted cereal crop such as rye or triticale chopped for silage. Taking one spring cutting from an aging alfalfa stand is another option. Then plant BMR sudangrass when the soil temperature reaches 60-65°, take two or three cuttings and replace it with oats, barley or annual ryegrass that can be chopped or grazed in fall.

“The goal is to produce as much tonnage as possible in that year on those acres,” says Robison. “I believe there’s room for 10% of your acres to have that type of program every year.”

Sawall planted BMR sudangrass June 13 with a no-till drill after taking a cutting of winter-damaged alfalfa. He sprayed the fields with glyphosate, applied 100 lbs/acre of urea and planted 42 lbs of sudangrass seed per acre. The recommended rate is 35-45 lbs/acre, he says.

About a third of the alfalfa plants survived the winter, so he used a low glyphosate rate to kill the grasses and stunt the alfalfa, hoping the legume would recover in time to improve the first-cutting yield. That cutting was mostly sudangrass, but he was expecting to harvest more alfalfa in the second cutting.

Ninety-degree days and ample moisture got the crop off to a fast start. Sawall’s seed salesman told him he should have 40” of forage in 40 days, and that the second cutting should be 30” tall 30 days later. He did better than expected on the first cutting. Cool weather initially slowed regrowth, but the crop was 40” tall and ready to be cut again 40 days later.

The dairyman was a little disappointed in the amount of forage remaining after the first cutting dried enough to be chopped and bagged.

“I think it’s kind of like corn silage without any cobs,” he says. “It takes a lot of corn to fill a wagon.”

Still, he expects to get more tonnage from two cuttings than he could get from silage corn planted in June.

“As an emergency crop, I think it’s a really good deal,” says Sawall.

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