Desiccant options for grain sorghum are more limited than other crops. Basically we are limited to glyphosate or sodium chlorate. Aim herbicide can be included with another material where morningglory vines are dense enough to interfere with the combine. Gramoxone is not labeled for desiccation of grain sorghum.
Glyphosate products: apply only after seed have reached 30% moisture content or less and harvest is at least 7 days out. Rates are from 32 oz to 64 oz/A in 10 to 20 gallons water per acre by ground or 3 to 10 gallons water per acre by air. Glyphosate is a slow acting material and has not been shown to measurably reduce seed moisture in small plot research. It should not be used on sorghum grown for seed production.
Sodium chlorate products: apply 7 to 10 days before harvest at labeled rate. There are a number of products available that have different rates of active ingredient. Consider using the higher recommended rate if applying when weather is cloudy and/or damp.