Sorghum may become an important crop option for Southern farmers looking to capitalize on what observers hope is a growing biofuels industry. New crops add diversity to areas that have depended on one or two farm enterprises and help farmers manage risks in a volatile market environment.
And adding grain, forage or sweet sorghum as a rotation option should improve yield potential for traditional Southern crops.
Oklahoma State University agronomist Chad Godsey is looking at several cropping systems and production techniques to help farmers manage what may be new crop options. “We're looking at forage sorghums, sweet sorghum and grain sorghum,” Godsey told a biofuels field day crowd recently at the Oklahoma South Central Research Station in Chickasha, Okla. “Forage sorghums are typically grown for cattle feed or for grazing,” he said.
Farmers in the Southwest have limited experience with sweet sorghum. “We have very little data on sweet sorghum. Farmers in the Southeast plant limited acreage for syrup.”
One of Godsey's goals is to determine how wide a window of opportunity exists for planting forage and sweet sorghums and still harvest as much biomass as possible. He said an April 15 through early July planting date for forage sorghums seemed to have little effect on yield. Waiting later to plant grain sorghum, however, was not advantageous. Late planting resulted in pollination during hotter parts of the summer.
He's also looking at nitrogen rates, row spacing, and plant populations for best biomass yield. “Sweet sorghum optimum nitrogen rate is about 100 pounds of nitrogen per acre,” he said. “It utilizes nitrogen efficiently, but if we remove 20 tons of biomass from a field we have to replace nutrients for the next crop.”
He said sweet sorghum likes “thick stalks to yield more juice. About three to four plants per foot of row has been standard for the Southeast. Visual observations indicate for non-irrigated fields, three to four plants are about right.”
Typically, row spacings have been at 30 inches or 40 inches, but Godsey also is considering narrower rows, 7.5 or 15 inches. “It looks like 15 inches may offer more tonnage, but that's only from one site and one year of data. We need more study.”
He said irrigated tests at several locations show an advantage to supplemental water. “But most locations the past two years have not been stressed. We really don't know how well sweet sorghum will do under drought stress. But throughout most of Oklahoma, we expect to see a benefit from irrigations.”
Godsey said sorghum offers a good fit with other cropping systems and should improve productivity on most crops, especially winter wheat.
“In the area west of I-35, we usually see continuous winter wheat,” he said. “Yields average about 30 bushels per acre and that is a flat trend. Lack of crop rotation is a key. Crop improvements have compensated for lack of rotation for years, but the only way to increase production is with rotation.”
Godsey said data under development from north Texas to North Dakota indicate that crop rotation, “regardless of the crop, will add 10 to 20 bushels per acre. We should see that in Oklahoma wheat (with rotation).”
Sorghum, he said, would be a good rotation option, “a good fit, and a crop with good water efficiency. We know we can grow grain sorghum and know that it fits our system. A market will be the driving force.”
He said markets have increased interest and acreage for sunflowers and canola. “We hope to see it work for sorghum as well.” Biofuel demand may be the catalyst.
Godsey said a sorghum rotation offers several advantages. “It's a summer versus a winter crop so we can concentrate on broadleaf weeds instead of grass weeds. We can control winter weeds in sorghum.”
He said some farmers could double-crop sorghum behind winter wheat. “We're going to look at that option next year. We've done more work in grain sorghum the last few years compared.”
But much work remains. Godsey said varieties available for some of the forage types and especially sweet sorghums are older. “Most are coming from Mississippi State University. The seed supply may be tight and that's one negative. It will be difficult to build an industry over night.”