New BMR forage sorghums compete with corn silage on digestibility, yield and growing costs.
In Florida, the old joke is that farmers measure corn silage yields in tons per acre and forage sorghum yields in board feet.
But new, highly digestible brown midrib (BMR) varieties of forage sorghum change all that. Plus, yields are starting to rival that of corn silage, water usage is much less and growing costs are just a fraction.
The crop's one drawback is that it needs 60°F soil temperature to germinate and a 95-day window between planting and a hard frost to produce full tonnage. The cutoff point is typically the southern borders of Wisconsin and Minnesota.
But for Southern growers, BMR sorghum deserves a look-see, say Extension agronomists. In Texas, where water is a precious and expensive commodity, some 40,000 acres of corn silage have been converted to forage sorghums in the past five years.
"Sorghum silage is a viable source of high-quality silage for the dairy industry in the Texas Panhandle,” says Steve Amosson, an Extension economist with Texas A&M University. The conversion to BMR sorghum silage has increased net returns by nearly $5 million/year relative to other forages in Texas alone, he and colleagues estimate.
"BMR sorghum works quite well, and we can replace corn silage on almost a one-to-one ratio,” says Rick Lund-quist, a dairy nutritionist who consults across the South.
The crop works especially well in double-cropping situations in Arizona, where irrigation cost is always an issue. Producers there typically plant corn silage as a first crop, then come back with sorghum as a second crop in June.
"By then, we're into the hot part of the season, so corn silage doesn't do as well and puts on a lot of fiber. The BMR forage sorghums don't,” Lundquist says.
The BMR sorghums also work well in grazing situations where annuals are used. Last year, Matt Clark of Blackstone, Va., planted strips of 11 forage types for his herd of 230 cows. He then fenced off grazing sections perpendicular to the strips to gauge cow preferences.
"Cows went to the BMR sorghum and sudangrass hybrids and just picked over the others,” he says. "They probably would have eaten the other forage if we'd fenced by forage type. But looking at tonnage and digestibility, the BMR sorghum was definitely better.”
Chris Teutsch, an agronomist with the Southern Piedmont Agricultural Research and Extension Center at Blackstone, tested forage samples from the strips as well. "The BMR types tend to be more digestible,” he says.
But he also notes significant differences between BMR sorghum varieties. "People should ask the seed companies if they have university digestibility data,” he says.
In Texas research completed five years ago, economics slightly favored corn silage—due to higher tonnage yields. But total direct expense for the forage sorghum was two-thirds that of corn silage: $375/acre for sorghum, $560/acre for corn silage. Irrigation and seed costs were big factors. Irrigation ran $90/acre for sorghum and $150/acre for corn silage. And while BMR sorghum seed runs about $15/acre, corn seed can now exceed $100/acre.
More on BMR nutrition
Brown Midrib Sorghum in Diets for Lactating Dairy Cows