Malting barley requires care when drying, in storage
Malting barley needs special care when drying and storing it, according to North Dakota State University Extension grain drying expert Ken Hellevang.
“Malting barley germination will be lost if the allowable storage time is exceeded,” he says. “For example, the germination will be lost in about 30 days if 17% moisture barley is stored at 70 degrees.”
The allowable storage time (AST) is cumulative, so if the barley is stored for 15 days at 17% moisture and then dried to 13% moisture, the remaining allowable storage time is only 135 days, rather than the 270 days of storage time if the barley had dried to 13% before harvest. Germination will be lost before mold growth is visible.
Malting barley germination also will be lost if adequate airflow is not provided to barley being dried by natural-air or low-temperature drying so that it is dried within the allowable storage time, according to Hellevang, Extension agricultural engineer.
The minimum recommended airflow rates and drying times to dry the barley within the allowable storage time are 1.25 cubic feet per minute per bushel (cfm/bu) to dry 18% moisture barley in about 16 days, just barely shorter than the AST of 18 days; 1 cfm/bu to dry 17% moisture barley in about 19 days, just barely shorter than the AST of 25 days; and 0.75 cfm/bu to dry up to 16% moisture barley in about 23 days, less than the AST of about 50 days, based on typical August weather conditions.
“Drying occurs in a zone that moves from the bottom of the bin to the top if the air is pushed up through the barley,” Hellevang says. “Grain at the top will stay near the initial moisture content until the drying zone reaches the top of the grain, so adequate airflow to dry the barley within its allowable storage time is critical.”
Use a fan selection program or table, such as one available from NDSU Extension, to determine whether you have adequate airflow. For more information, go to NDSU’s grain drying, handling and storage website (https://www.ag.ndsu.edu/graindrying). You also can have the fan supplier verify the airflow rate.
The time required to complete drying and the allowable storage time will be longer at cooler temperatures because the cooler air holds less moisture. Drying grain at 60 degrees will take about 30% longer than it does at 70 degrees.
Adding supplemental heat to a natural-air drying system will reduce the moisture content of the grain but only reduces the drying time slightly. Warming the air by 5 degrees will reduce the relative humidity by about 10% and the barley moisture content by about 1.5 percentage points. The air normally will be warmed 3 to 5 degrees by the fan operating at a static pressure of about 5 to 6 inches associated with drying barley, so typically, little additional heat is needed.
Adding more heat than is required results in the barley being dried to a moisture content lower than desired. The equilibrium moisture content for barley is about 12% at 70 F and 60% relative humidity, which are average conditions for August. North Dakota’s September air conditions of 58 F and 70% relative humidity will be 63 F and 60% relative humidity if the fan heats the air 5 degrees. This air will dry barley to about 12% moisture content.
Hellevang also recommends limiting the plenum temperature in a high-temperature dryer to a maximum of 110 F when drying malting barley to maintain germination.