As drought and water issues continue to threaten forage production, the use of sorghums – which need less water than corn and survive in hot and dry conditions – is more than a growing trend. It’s a necessity, say several experts.
Although there’s a known sorghum belt from Texas to southern South Dakota, the crop is being boldly tested and grown in areas where it hasn’t been grown before.
Sorghum comes in several types that are used for several purposes.
Grain sorghum is utilized for animal feed in the U.S. and human consumption worldwide. Forage sorghum is grown for silage and greenchop, while sudangrass – yes, it is a sorghum – is used for hay, silage and grazing. To further complicate matters, hybrids of sorghum and sudangrass, appropriately called sorghum-sudangrass, can be cut for hay or silage or be grazed.
Then there’s sweet sorghum, grown for molasses or syrup production, and the new kid on the block, high-biomass sorghum, was recently developed for renewable bio-products.
But sorghums are attracting the most notice as livestock feed. The past 30 years, plant breeding has increased the crops’ yield, quality and digestibility. Equally important, half the water is needed to produce a ton of sorghum silage vs. a ton of corn silage, according to university studies. Some researchers are more conservative, saying sorghums are a third more efficient than corn.
Sorghums aren’t new. They “disappeared” in California in the late 1960s and early 1970s, says Jeff Dahlberg, director of the University of California Kearney Agricultural Research & Extension Center.
“Now we’re trying to rediscover the crop in the state,” he says. “This is something we seriously have to look at as water is going to be a major limiting factor in a lot of our ag production. We are trying to introduce more of our producers to forage sorghums and grain sorghums.”
“Forage sorghum has traditionally been widely used in the South and Southwest,” adds Ricky Rice, Winfield Solutions’ forage product manager. “With some of the improvements, we’re seeing that market expand up into the Midwest and into other areas.”
The Upper Midwest helped increase sorghum sales last year when growers there needed a fast-growing, high-yielding forage to take the place of winterkilled alfalfa and grasses.
In the short growing season of the Northeast, even into southern Canada, sorghums can be grown as summer energy crops between winter forages such as triticale and provide “excellent” dairy feed. So says Tom Kilcer, an agronomist and former Cornell University Extension agent.
“We’re pulling off two crops on one acre,” says Kilcer, now an independent crop advisor at Kinderhook, NY. On ground that could produce 22-24 tons/acre of corn silage, he’s seeing 30-ton/acre yields from the triticale-sorghum double crop.
“We’re going to have weather that’s more like the 1930s (Dust Bowl); we’re going to have more variability, and we need to be able to consistently produce forage. By getting two crops instead of one, our risk is now spread out,” Kilcer says.
Tolerant To Drought
Growers need to start thinking about how much water they’ll use in a cropping system, adds Virginia Tech forage specialist Chris Teutsch.
“Drought’s a major issue. When we get into highly erodible soils we find in the Southern Piedmont region of Virginia, drought is an issue we face year in and year out.”
Teutsch has been studying how corn and sorghum can be grown together to increase drought tolerance of the silage crops. Forage sorghum added to late-planted corn doubled the yield of the silage crop in the first of two years of trials and tripled the yield in the second year.
“Adding as little as 4-6 lbs/acre of forage sorghum really increased the drought tolerance of that corn crop,” he says.
The Southwest, meanwhile, is “seeing an increased interest in anything that is potentially drought-hardy,” says Mark Marsalis, New Mexico State University Extension forage specialist.
Mature forage sorghum, like this inspected by Mark Marsalis, New Mexico State University Extension forage specialist, forms grain heads. Nutritionists, however, find it challenging to deal with the grain portion of the crop, which doesn’t process like corn kernels, much of it passing through the cattle that consume the feed. Photo: NMSU Ag Science Center, Clovis
“This drought has got everybody scrambling and looking for alternatives to what they’re currently doing. The water situation, especially in eastern New Mexico, where dairies are located, and West Texas, is driving several producers to really start looking at some of the forage sorghums a lot harder and incorporating more and more acres into their silage operations.”
Sorghums show the greatest potential where water has become marginal for corn due to reduced well capacity, he adds.
But sorghums – especially forage sorghums – have some hurdles to clear, says Steve Martin, a Fort Collins, CO, nutritionist with Dairy Nutrition and Management Consulting, LLC.
“Alfalfa and corn silage are the queen and king of dairy feeds, and some dairymen think that sorghum doesn’t even have a seat at the royal table. That’s a mindset that we need to change,” he says.
Forage sorghums offer flexibility in planting, multiple harvests and produce a variety of feedstuffs, says Martin. Sorghum silage can provide abundant fiber to help produce butterfat and maintain cow health, he adds.
What it isn’t providing, at least not in a consistent or quantitative manner, is starch. Yet some producers believe they can replace corn silage with highly digestible brown midrib (BMR) forage sorghum silage, Martin says.
“Comparing BMR sorghum to corn silage is like comparing pickups to tractors. They’re different parts of the diet,” he contends.
Corn silage offers well-fermented, palatable stalks and leaves and high-quality, high-moisture kernels processed for their starch.
“But when you correctly feed BMR sorghums, they are actually a little bit more of a competitor of the alfalfa in the diet than the corn silage. You can’t deny the fact that, if I take out 20 lbs of dry matter corn silage (from a ration), I take out 10 lbs of corn grain. I can’t put in 20 lbs of BMR sorghum no matter how good the forage digestibility is.”
Forage sorghums do contain quite a bit of starch – the problem is that, as with corn, the starch is held hostage in the kernels. Corn kernels can be processed or cracked to release their starch. At this point, there isn’t a mechanism to mine the starch from the sorghum “BBs,” as Martin calls them. An unknown amount of them pass through cows and can be found in their manure.
A logical solution should be to harvest the sorghum when the kernels are soft and less mature. But New Mexico’s Marsalis, who has done quite a bit of research on sorghums, says fields hold “a whole spectrum of grain maturity, even on one plant. Even when grain on the plant is approaching maturity, the whole-plant moisture may be up in the 75% range, and you want it to be around 65-70% to put it in a pit.” So harvesting at an earlier maturity isn’t always reasonable, he says.
Forage-quality tests of sorghums are misleading as well, Martin says. Finely ground samples test higher in starch than will actually be digested by the cow. He’s working with colleagues to develop a way to accurately determine starch availability on sorghum silage, and he’d welcome a way of processing the kernels.
Produce High Yields, Quality Forage
Dahlberg’s California research indicates that forage sorghums can offer quality and high yields – up to 36 tons/acre – on 19” of irrigation water and 125 lbs of nitrogen (N).
“Two of the biggest mistakes in using forage sorghum is that we overwater and put too much fertilizer down. What happens is, the plants grow like wildfire and they will lodge.
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