Sorghum acres to grow due to drought tolerance, new varieties

By Susanne Retka Schill | December 27, 2012

Sorghum is poised to come into its own as an alternative to corn. It proved its mettle in the 2012 drought, producing decent dryland yields with very little rainfall. And, with the U.S. EPA approving a pathway for grain sorghum-to-ethanol as a conventional biofuel, and even as an advanced biofuel when combined with other greenhouse gas (GHG) reducing technologies, a big new market looms.

Ismail Dweikat, sorghum geneticist and the University of Nebraska-Lincoln, explained that sorghum goes into dormancy under severe drought and has several mechanisms to conserve moisture, waiting for rain. He cites a field near Wilbur, Neb., that got 2 inches of rain on June 14, followed by eight weeks with zero moisture. Rain finally came at the end of September—too late to help the corn in the adjacent field. The grain sorghum, however, utilized that moisture to resume growth and went on to yield 100 bushels per acre.

The dormancy strategy is one of many the drought-hardy plant employs. Sorghum also generates more roots in dry conditions, to enhance the plant’s ability to search for water. It has wax on its leaves and stems to reduce moisture loss, as well as narrow leaves and the ability to fold the leaves in on themselves – all strategies to conserve moisture in both heat and drought stress. “Sorghum uses one-third less moisture than corn and it takes one-half the water of sugarcane,” Dweikat said.

Sorghum has been greatly overlooked, according to Dweikat, partly because it has an image as a poor man’s crop, “while if you can grow corn, you’re a first-class farmer,” he explained. Sorghum has also lost out due to its late planting window—a month later than corn. “Imagine being a farmer the first week of April looking out your window watching your neighbor planting corn. It can make you anxious,” he said.

On the positive side, not only is sorghum drought resistant, it has significantly lower input costs than corn. While corn can cost $150 to $200 per acre for seed, sorghum will cost $25 per acre to plant, Dweikat said. It is known for having low fertilizer requirements as well, although if given the same fertilizer and water inputs as corn, grain sorghum’s yield will equal corn. “There are farmers in the contests getting 280-300 bushels per acre,” he said. Sorghum can be planted and harvested with the same equipment as corn, and contains the same amount of starch, meaning it handles and yields the same as corn in the ethanol process.

Researchers have been targeting sorghum’s limiting factors, one of them being poor weed control options. New varieties are within a year or two of release that incorporate traits for ALS-inhibiting herbicide tolerance. Sorghum is not a candidate for glyphosate-tolerance traits, he added, due to the potential for the resistance to move into closely related problem weed species.

New hybrid lines are also solving the cold tolerance issue. While traditional varieties need 70 degree Fahrenheit soil temperatures in order to germinate, the new varieties will germinate at temperatures closer to 50 F, similar to corn, as well as mature in a shorter growing season. “”We’ve been working on developing sorghum lines you can grow in Montana, North Dakota and even Canada,” Dweikat said. While increased cold tolerance will move the crop north, it could also facilitate double cropping in the South, removing some of the concerns with winter frost tolerance.

In sweet sorghum development, new hybrids have solved the problem with sweet sorghum having low seed set on difficult-to-harvest tall stalks. “The mother lines of the new sweet sorghum varieties are short enough to harvest with conventional equipment,” Dweikart said.

He is enthusiastic about sweet sorghum’s potential use as a biofuel feedstock, pointing to the 1.5 million hectares (3.7 million acres) being planned for Brazil. Sweet sorghum processing and conversion is compatible with the sugarcane process, he said, and the sweet sorghum harvest could be timed for the off-season of sugarcane, to facilitate year-round ethanol production. Sweet sorghum is being considered as a season-extending crop in other countries looking to expand ethanol production, he added, such as India and the Philippines.

In the United States, sweet sorghum is being considered in areas of the south where multiple crops could be grown. “In Florida, a group near Orlando is working on getting 2.5 to 3 crops of sweet sorghum a year,” he said. Because sweet sorghum is grown for its sugar-containing stalks and not grain, it requires even less water and less nitrogen than grain sorghum, he added. Southern growers are also expected to look at sorghum, both sweet and grain, as an alternative to cotton, which is likely to lose its subsidies in the next Farm Bill.

A big expansion in sorghum acres won’t happen in a year, as it can with corn or soybeans, due to fewer acres being grown and less seed availability. The newest hybrid and inbred developments need another year or two for testing and selection as well. Dweikat said he’s encouraged by two Texas seed companies that have contacted UNL to acquire hybrid and inbred lines for their sorghum lines.

Interest in sorghum is definitely picking up, he added. “I was at the American Seed Trade Association meeting recently in Chicago, and for the first time, we had the largest crowd in the sorghum presentations.”


For more on sorghum developments in the ethanol industry:

Partnership produces ethanol from sweet sorghum in Kentucky 

Grain sorghum well received in California trial   

EPA publishes final rule for grain sorghum fuel pathways

Companies advance sweet sorghum as ethanol feedstock in Brazil