When Guy Clark first planted brown midrib (BMR) sorghum-sudangrass eight years ago, he put in 80 acres. Today he has 400 acres of it and only 60 of alfalfa.
“I kept plowing old hay land under and planting brown midrib,” says Clark, who milks 400 cows near Watertown, NY.
He likes growing and feeding BMR sorghum-sudan for several reasons. First, he says, “It's a cheap crop to put in. We don't use any commercial fertilizer and I don't spray it. It grows so fast the weeds don't stand a chance.”
Clark's liquid dairy manure provides the needed nitrogen. In 2004 he got enough silage from three cuttings to feed his cows for a year.
In New York, BMR sorghum-sudan yields about the same as silage corn, says Tom Kilcer, Rensselaer County extension agent. Yields can at least equal those of corn on less-productive corn land and when corn planting is delayed due to wet fields, he adds.
“On a heavy clay soil, it also grows a lot better than corn,” says Clark.
Although the annual grass is a warm-season crop, it does well almost anywhere in the U.S., provided it's planted when soil temperatures are 60° or warmer, Kilcer points out.
When planted in warm soils, it does well under wet conditions. But its performance when the weather turns dry is one of its strengths.
“When it becomes droughty, sorghum-sudangrass outperforms corn every time,” says Kilcer. “It's a drought-tolerant crop.”
Because the crop is planted in warm soils, the use of herbicides is greatly reduced. The need for insecticides is also reduced, because by the time the grass is planted, root-worms have hatched.
“They starve to death or are killed by the prussic acid,” Kilcer notes.
The grass also has environmental benefits. Kilcer says studies show that the fine root system and leaves of the fast-growing sorghum-sudan help reduce soil erosion by about half compared with corn.
However, sorghum-sudan won't grow well in saturated soils, or in prolonged periods of cool, wet weather.
Another major drawback is the amount of nitrogen needed to grow the crop. Without manure, 120-150 lbs of nitrogen are needed for each cutting. With manure, an additional 50 lbs per cutting are recommended. Other fertilizer requirements are similar to those for corn.
BMR sorghum-sudan silage can replace alfalfa hay, haylage or corn silage in a dairy ration. It tests about 15-16% protein, and has slightly less energy than corn silage.
When replacing corn silage with BMR sorghum-sudan, starch sources need to be added to the ration, and protein supplementation can be reduced slightly. When replacing haylage, especially low-quality haylage, Kilcer says grain volume can be reduced and protein may not need to be increased.
Clark particularly likes the fact that BMR sorghum-sudan is fiber-digestible. The digestible neutral detergent fiber (dNDF) of the grass is about 70%, whereas corn silage's dNDF is typically 53% and alfalfa averages 52%.
“The cows like it, so they eat more of it,” he says.
BMR hybrids are typically 5-10 percentage points higher in NDF digestibility than conventional sorghum-sudangrass hybrids, says Rick Grant, with the W.H. Miner Agricultural Research Institute, Chazy, NY.
One of the keys to succeeding with the grass is to feed a high-forage ration — over 55% of the dry matter. Because BMR sorghum-sudan is highly digestible, it needs to be replaced as it breaks down to maintain rumen health.
Clark feeds a mixture of alfalfa haylage and sorghum-sudan silage totaling 80% of his ration's dry matter — 60% sorghum-sudan and 20% alfalfa haylage.
“Overall, cows do very well on it,” Clark says. “We average 70 lbs of milk per cow, and it increases the protein and butterfat in the milk.”
Not all BMR sorghum-sudans are created equal, though. “Only BMR-6 has the same milk-producing ability as corn silage,” says Kilcer. The other two types, BMR 12 and 18, produce lower-quality forage.
In the Northeast, growers need to plant high corn populations, and should do the same with BMR sorghum-sudan, says Kilcer. He recommends planting 60-70 lbs of seed per acre in that region. On a per-bag basis, he says the seed costs 55-75% as much as corn seed.
Common mistakes include not harvesting at the optimal height of 36-42", not mowing in a wide swath to promote fast drying, not applying nitrogen in split applications, and not using a roller conditioner.
Despite those pitfalls, Kilcer says there's been a rapid increase in acreage over the past five years. Growers from Maine to Delaware and west to Wisconsin are trying it.
“It's also taking off with organic producers because they don't have to use herbicides,” he says.