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Potential bioenergy crops under study

Sorghum has been produced in the United States for several hundred years as a grain crop; it’s been a worldwide source of grain for much longer.

A hardy crop, drought tolerant and water efficient, sorghum provides a consistent source of livestock and human food. That consistency also makes it an ideal candidate for bioenergy production.

Researchers at Texas AgriLife Research in College Station are looking at various sorghum types and numerous hybrids to develop energy crops that provide consistent, high biomass production. Efforts include work on traditional grain sorghum hybrids, forage sorghums and sweet sorghum selections.

Forage sorghums may have the most potential for cellulosic ethanol production, says Bill Rooney, professor, soil and crop sciences. “Sweet sorghum accumulates sugar in the stalks, like sugar cane. Energy sorghums accumulate lignins and cellulose. They never flower and are more drought tolerant.”

Rooney is working mostly with forage sorghums to develop plants that create more biomass. “We’re looking for things that are even better than what we have,” he says. “Our plots include many hybrids and we’ll harvest and select the best ones.”

He says energy sorghums, a term he’s using to differentiate hybrids he’s selecting for increased biomass from sweet sorghums and grain producers, are photo period sensitive. “They produce biomass as an annual crop. We need annual crops in a bioenergy crop production program because we sometimes have winter kill (with perennials) and we need a consistent supply.”

A mix of both types may be part of an overall strategy and selection will be driven by ethanol production plant availability. “In my opinion, with sweet sorghums length of growing season will be a factor.” Primary adaptability could be in areas where sugar cane currently grows. He says sweet sorghums will have to be near processing plants.

“Energy sorghums will be more adaptable across the country” he says. “But that assumes cellulosic ethanol comes into play. Location still will be a key to get the product to end users.”

Rooney says breeding and development “is my job. We want tonnage, 10 to 12 dry tons per acre.” He’s working with a number of forage sorghums to develop a better energy plant.

“We change pollination and take the animal feed factor out of the equation. We want to make the stalks bigger and more pithy. Energy sorghum will produce more weight and more leaf for increased biomass.”

Rooney started working on energy sorghum development in 2003 and was working with other sorghum types back in 2001. He irrigates some of his plots, as much as 12 inches during the 2009 growing season. He planted in April and had one decent rain in mid-May.

Some of his selections towered several feet above his head and featured thick stalks. Other selections look more like typical grain sorghum plants.

Jurg Blumenthal, associate professor and Extension specialist, is looking at production strategies to improve energy crop management and help farmers adapt to new opportunities.

“Growth (of energy sorghum) is similar to hay grazer, a crop we haven’t seen much lately but is coming back,” Blumenthal says.

He says sorghum “fortunately, is a forgiving crop. We have relatively few issues with weed control, for instance. It’s a competitive crop and shades out weed competition.” Atrazine, applied pre-emergence, is about the best option available for weed control. Johnsongrass could be trouble, “but grain sorghum will compete with Johnsongrass.”

He says plant lodging is a concern and expects some harvest challenges. Insect pests — not so much. “We haven’t seen many problems with head moths. We don’t have many borer problems yet and we’re looking at sorghum all over the state, from the Gulf Coast to the High Plains.”

Blumenthal says moisture demand is a critical factor. “We’re looking at plots near Amarillo with irrigation. We were already looking at animal nutrition (with sorghum) and have branched off to consider energy crops.”

He says farmers can produce the same tonnage and quality with grain sorghum that they can with corn “but with less water. Yield expectations could be as high as 15 tons per acre. That equals a 300-bushel corn crop.”

Blumenthal says agricultural engineers are looking at harvest techniques and equipment. “The height and weight relationships are different from corn, so we’re looking for the optimal header. Storage also is an issue with energy sorghum.”

He says determining whether to store green or dry will be a concern. “That may depend on the customer. Transporting dry matter will mean lower transportation costs, but it takes time to dry down and we have to consider if we have enough rain-free days to dry.”

Shelf life may be an issue, too. “We can harvest dry and store it like we do hay.”

Russ Jessup, assistant professor, soil and crop sciences, is a grass breeder working on perennial bioenergy crops. He’s working with millets, Miscanthus and some switchgrass plots. “Perennial millets seem the most promising. Agronomics are fairly easy and energy companies like it,” he says. “Also, we’ve done work on forage millets here for 60 years. We have a lot of germplasm.”

Jessup says Miscanthus may produce “a large amount of biomass. We also have a lot of germplasm collected and we have a lot of plants in the field. Now, we’re in a development year. I’ve been here only since January, so we’ll evaluate plants next year.”

He says Miscanthus is a dual use crop, energy and grazing.

Blumenthal says a lot of producers have shown interest in growing energy sorghums. “Now, we need to build the first plant.”

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