I’ve gotten several calls this week asking “How late can we plant grain sorghum?”, “What kind of yield potential do we have when planting in June?”, and “What problems are we likely to face when planting this late?”. Many of the calls are relating to fields that may still be underwater from flooding and earlier plantings that have failed, leaving producers with contracts still to fill.
We have conducted grain sorghum planting date studies at Marianna for the last three years and have found that yields of irrigated grain sorghum planted in late May through June can still be good, but in general, yields dropped below 90% of full yield potential in mid-May. Four full-season hybrids were evaluated each year (Pioneer 84G62, Triumph 82-G, Terral 96H81, and Dekalb 54-00 or 53-67). Yields of later planted grain sorghum were variable from year to year due mainly due to extremes in weather, but yields as high as 100 bu/acre have been achieved and as low as 45 bu/acre where harvest was delayed by rainfall, resulting in poor grain quality. Grain sorghum planted the first week in July yielded approximately 40 and 80 bu/acre in both years of the trial.
Production Issues with June Plantings:
Insects: Insect pressure will be much greater when planting in June compared to April. In our studies, April planted grain sorghum on average has needed one insecticide application (for midge or headworms). When we get into June plantings, three insecticide applications have been typical, one or two for sorghum midge and one or two for headworms. Whorl feeders have also been problematic (corn earworms, fall armyworms) prior to heading some years.
Hybrids: I would plant full-season hybrids that we normally plant. We have plenty of growing season to still plant full season hybrids. Short season hybrids likely won’t have the yield potential that full season hybrids have. Grain sorghum hybrid testing results can be found at: http://www.arkansasvarietytesting.com/
Seeding Rates: Don’t get stands too thick. Keep in mind that emergence percentage should be much higher now with warm temperatures compared to earlier plantings. For irrigated fields, 90,000 seeds/acre is the recommended seeding rate, and for dry-land fields, 60,000 seeds/acre should be plenty of seed.
Harvest and Drydown : In the seven planting dates over the last three years that were planted from May 29th to July 8th, days from planting to harvest ranged from 98 days to 134 days with an average of 116 days. Rainfall at harvest and drydown conditions were the biggest factors in the differences between harvest days. Average moisture from these harvests was approximately 16%. One of the biggest problems, if not the biggest problem, with June-planted grain sorghum, is getting the grain to dry down to 14% moisture or less. Having grain bins and a way to dry the grain can be a huge benefit in years when grain won’t field dry to low enough levels to take directly to grain terminals.