Producers should be extremely cautious in holding high-moisture grain sorghum prior to drying. High-moisture grain sorghum packs much tighter than high-moisture corn. This inhibits air circulation within the grain and can result in heating, molding and sprouting problems. Never hold wet sorghum longer than 2-4 hours unless aeration is provided.
Continuous flow or batch dryers are the preferred methods for drying grain sorghum. If it must be dried in a bin, the bin should be used as a batch-in bin dryer, limiting the drying depth of each batch to 4 feet. After drying, cool the grain and move it to another storage bin before the next day’s harvest. A 3-foot depth of sorghum is equivalent in resistance to a 4-foot depth of corn at an airflow rate of 10 cfm. An individual seed of grain sorghum will dry faster than an individual seed of corn, but greater flow resistance from a bin of sorghum will reduce the airflow. As a result, the drying time for grain sorghum is longer than for corn. Cooling time is also longer.
Optimum drying temperature depends on the type of dryer, airflow rate, end use i.e., feed, market, seed, and initial and final moisture contents. The maximum temperature for drying grain sorghum for use as seed should not exceed 110 F. Dry for milling below 140 F in high airflow batch and continuous flow dryers and 120 F in bin dryers. If used for feed, drying temperatures can be up to 180 F. Always cool grain to within 5-10 degrees of the average outside air temperature after drying. Natural, unheated air may be used when the relative humidity is 55% or less and the grain moisture is 15% or less.
Natural, unheated air drying can be used to dry grain sorghum if the moisture content is 16% or below and the drying depth is less than 10 feet. Drying fans must be capable of delivering at least 1-2 cfm/bushel. Because the drying process is slow, it is important to start the fans immediately after the floor is covered.