A sweet solution to the nation's energy dependence may be a good fit for Texas farmers.
“Sweet sorghum is a promising renewable fuels crop for our producers,” says Texas A&M Extension agronomist Juerg Blumenthal.
Blumenthal spoke at a recent renewable fuels conference in Belton, Texas, and said if the country wants to reach its optimistic energy goals and independence we have “to go beyond the current standard of grain to ethanol.”
He said forage and sweet sorghums may help bridge the gap.
“We can make energy from many bio-mass sources,” Blumenthal said. But sweet sorghum provides a liquid crop for fuel. Ethanol plants extract the juice to make fuel. It's a sugar to energy source instead of a celulosic source, which is a bit more complicated.
He said sorghum fits well into a Texas cropping system for several reasons.
It offers high yield potential.
Texas farmers have experience producing sorghums.
It is a water efficient crop. “We have a conflict if we use a lot of energy to irrigate to produce energy.”
The harvest technology and equipment is already in place.
Blumenthal has researched several types of forage and sweet sorghum hybrids and will look at some exotic sorghum germplasm in the future.
He said one advantage of some sorghum hybrids is that they are not photoperiod sensitive. “They will flower when daylight is less than 13 hours a day.”
His primary goal was to evaluate forage and sweet sorghums for bioenergy production in Central and East Texas. He used small plots on the Texas A&M farm in the Brazos Bottoms and conducted both dryland and irrigated trials.
He used 100 pounds of nitrogen initially and applied another 100 pounds after the first cutting. “Another advantage to sorghum in Texas is the second crop,” he said. “In some areas we may be able to get a third cutting.”
Blumenthal used atrazine for weed control and sprayed one or two times for armyworms, primarily to control pests in the second crop. “We make the first cut in July and make one or two treatments on the second crop,” Blumenthal said.
He said sudangrass and sorghum sudangrass showed some lodging problems with the first harvest. “The photoperiod sensitive lines stood up well. And lodging was not an issue in the second crop because growth slowed.”
The first crop, photoperiod sensitive and sweet sorghums, averaged as much as 7.5 tons of dry matter. The second crop yielded 60 percent to 70 percent of the first crop. “That's still as much as five tons of corn,” Blumenthal said. “We also saw a response to irrigation.”
He said sugar production potential is significant with juice yield up to 15 tons per acre.
“Sweet sorghum juice production was very high; sugar content of the photoperiod sensitive sorghums was less.”
He said the sweet sorghum produced “an impressive second crop.”
Ethanol yield from the first cutting averaged 200 gallon per acre with the second crop “still high but less than 150 gallons per acre.”
Blumenthal said the highest yield in the trial was 12.4 tons of dry matter per acre. Highest ethanol production came from sweet sorghum and hit 395 gallons per acre. He said that production would equal about 147 bushels of corn per acre with a conversion efficiency of 2.7 gallons per bushel.”
“Sweet sorghum production exceeds the average yield for irrigated corn, 125 bushels per acre. We figure 12.8 tons of dry matter equals a 294-bushel per acre corn crop.
He said sorghum production makes more sense for East and Central Texas than a biomass crop such as switchgrass, which performs better in the plains. “Sorghum fits better into our production systems,” he said. “With switchgrass, producers have to commit to multiple years.”
Sorghum allows growers yearly options.
“Sorghum seems to be a good fit for Texas.”