The first question for Scott Staggenborg, director of technical services at Chromatin, during his presentation at Sorghum U in Mitchell, S.D., was about tannins in grain sorghum. Staggenborg was asked if all grain sorghum varieties in the United States contain tannins.
The simple answer is no. Staggenborg said that 99 percent of the grain sorghum varieties in the U.S. do not contain tannins, and grain color has nothing to do with tannin content. Grain sorghum varieties with tannin are grown in Mexico and South America
“But in the U.S. you cannot buy a commercial hybrid that has tannins in it,” Staggenborg said. “We at Sorghum Partners have varieties with tannin in them, but we don’t sell them in the U.S.”
The big problem with tannins is that when they are fed to animals or used to produce ethanol they tie up proteins. Even though there are studies that show feeding a small amount of tannin will increase feed conversion rates, if used too much the efficiency goes down. Staggenborg said studies have shown that if tannins are put into an ethanol production process, it ties up proteins and causes problems with microbial activity.
“It used to be that 90 percent of the grain sorghum grown in this country went to feed cattle; now a big chunk of it goes into ethanol production and both of those systems don’t want tannins,” Staggenborg said.
Tannin has a bitter taste, which is why birds don’t like it. Preventing damage from birds is one reason tannin varieties are popular in South America. It is traditional for those growers to use tannin varieties.
“We grow it all over the U.S. and don’t worry about bird damage,” Staggenborg said.
Staggenborg also was asked if all grain sorghum varieties will tiller. Grain sorghum does have the ability to tiller in certain growing conditions.
“Corn is very straightforward typically with one plant and one ear,” Staggenborg said. “But with sorghum, tillering is one way it adjusts.”
If grain sorghum is planted too thin, it might adjust by tillering. The follow-up question for Staggenborg was whether growers should want their sorghum to tiller.
“I think you do want it to tiller,” Staggenborg said. “We as an industry are in favor of tillering, but you up here in a short-season environment should not encourage tillering.”
Tillering is a function of seed population and temperature. Staggenborg said tillering is a mismatch between temperatures. When there are cool temperatures, the development rate is slowed and the photosynthetic rate stays the same. The development rate is controlled by temperature.
“What happens is the plant is making all kinds of carbohydrates, but it can’t put it anywhere because those leaves are just developing so it diverts those carbohydrates into a tiller,” Staggenborg said.
The problem is these tillers can be three days behind the rest of the plant. That is not a problem in Kansas because there is a longer growing season, but in South Dakota it could be a challenge with a shorter growing season. Staggenborg said instead of depending on tillers to boost total seed count, maybe growers in South Dakota should consider higher planting rates. Planting rates of 70,000 seeds per acre or more might be an option.
“The beauty of sorghum is that it is very forgiving,” Staggenborg said. “I have very seldom stood next to a field of grain sorghum and said you better replant this field.”