Seeding rates and insects are two issues sorghum growers should watch closely if flooding or other storm damage has forced them into June plantings, said Jason Kelley, Extension wheat and feed grain specialist for the University of Arkansas Division of Agriculture.
Kelley said three years of planting tests at Marianna, Ark., found that the highest yields were for plantings in April.
“Yields of irrigated grain sorghum planted in late May through June can still be good,” he said, adding, “Yields dropped below 90 percent of full yield potential when planted in mid-May or later.”
There is still hope for late-planted sorghum.
“Grain sorghum planted in June has yielded 45 to 100 bushels per acre and grain sorghum planted the first week of July yielded approximately 40 and 80 bushels per acre in two years of trials,” he said.
Kelley warned insect pressure would be much greater in June than April.
“In our studies, April-planted grain sorghum on average needed one insecticide application for midge or headworms,” he said. With June plantings, “three insecticide applications have been typical, one or two for sorghum midge and one or two for headworms.”
Whorl feeders such as corn earworms and fall armywoms have also been problematic before heading some years.
Seeding rates are a key — and Kelley warned against planting too densely.
“Emergence percentage should be much higher now with warmer temperatures than earlier in the year,” he said.
Kelley recommends 90,000 seeds per acre for irrigated fields and 60,000 seeds per acre for dryland fields.
Kelley’s test results are available at http://www.arkansas-crops.com/2011/05/26/how-late-can-we-plant-grain-sorghum/.