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February 16, 2001
New forage sorghum
varieties show promise
By Lana Robinson
Field Editor
New forage sorghum varieties—one that never forms a seed head and another that is more digestible—promises improved grazing and silage yields for blackland producers. Both the potential benefits and drawbacks of new forage sorghum varieties were reviewed in detail in a forage session at the recent Blacklands Income Growth 2001 Conference in Waco.
Developed and released commercially in the last few years, photo period sensitive (PPS) forage sorghum and brown mid-rib (BMR) forage sorghum are news to many growers. PPS sorghum does not form a seed head until day length is less than 12 hours and 20 minutes, reserving its energy for forage growth. For blackland producers, this means PPS sorghum will have vegetative growth for six months. Planted in early April and irrigated, PPS sorghums have produced 45 tons and more per acre during a six-month growing season.
"You cut it, graze, bale it, ensile it, use for windbreaks or green manure throughout the six-month period," said Walter Moss, president of the Walter Moss Seed Company and chairman of the B.I.G. forage session.
Brown mid-rib sorghum has a lower lignum content—from 40 to 60 percent less—than conventional sorghums. It offers improved dry matter intake and digestibility.
It is also high in protein but uses less water than corn. Some of the earlier BMR releases had a tendency to lie down, but newer varieties have good standability, Moss noted.
"Roughly, its food is equal to corn silage, but with one-third the water," he said.
Brown mid-rib gets its name from the fact that the central leaf vein is not green like other sorghums but brownish red.
Dr. Fred Miller, sorghum breeder and professor emeritus at Texas A&M University, who presented the program, said a major advantage of PPS and BMR forage sorghums is their versatility.
"You can do many different things with them. They're not for silage only, or direct pasture only or for hay only. You can do all three," he said.
Miller said you plant BMR sorghum at the same rate as regular sorghum and sudan. BMR is well-suited to alkaline, droughty or saline conditions. The brown color, he said, is only a marker.
"BMR decreases by-pass protein losses. Yield, RFV (Relative Feed Value), lodging and type are different among BMR hybrids. If you look at the RFV, you can see why all forages are not created equal," he said, noting that the TDM values are greater for BMR. "Don't produce yield. Produce quality."
According to Miller, these sorghums do not have a boot stage. In trials, the forages were harvested at 60, 70 and 80 days to determine the breakeven point on yield and quality.
"It appears that about 70 days after planting is the time to cut if it's going to be for hay—less for direct pasture," Miller said. "These sorghums have good regrowth capacity, a good root system and fertility, with superiority of a 70-day harvest. You can blend your own material in your planter box, put BMR with a conventional forage you've had good luck with, and you're going to come out ahead."
Miller noted differences in regrowth capacity in the silage types. He said BMR had the lowest yield, but more energy is harvested from it through the cow than the others. In the 2000 Bushland trials, when given a choice, 68 cows ate the photo period sensitive and BMR silage first.
"Forty-five percent is pretty good for digestibility. The BMR was 69.6 percent," Miller reported. "Cows are pretty smart."
In terms of milk yield on a per-acre basis, Miller said 13-ton BMR silage will produce the same amount as 15-ton corn silage. He attributes that to the protein by-pass.
"Also, the cost of planting sorghum is less than corn. It uses about the same amount of fertilizer, but a third less water to produce 1 lb. of dry matter under any situation than corn. Farmers must pay attention to what we use water for. Insecticide costs are considerably less with sorghum. And with sorghum, we have diversity," he said.
