Equilibrium Moisture Contents for Grain

Sam McNeill, Extension Engineer, University of Kentucky

Implications for drying:

• Grain will eventually reach the moisture levels shown in the tables when exposed to the corresponding temperature and humidity levels for long periods of time. This can occur in the field or in the top layers of a low-temperature bin dryer.
• Drying time will depend on the airflow rate through grain, which in turn depends on the depth of grain in a bin. The minimum drying rate for natural air drying is 1 cfm/bu, but this can take up to a month to dry the top layer depending on the grain and air conditions--during which time spoilage can occur.

Implications for storage:

Moisture Content Charts

Chad Lee, Extension Agronomist, University of Kentucky

A grain moisture chart was just updated for producers this fall. Dr. Sam McNeill calculated the Equilibrium Moisture Content (EMC) for corn, soybean and wheat. The charts identify the moisture that each seed will approach at a certain air temperature and relative humidity. For example, corn will approach 11.3% moisture content at 70 degrees Fahrenheit (21.1 degrees Celsius) and 50% relative humidity. Soybeans will approach 8.8% moisture content at 70 degrees Fahrenheit and 50% relative humidity.

Click here for the EMC chart.

Drying the 2011 Corn and Soybean Crops

Sam McNeill, Extension Agricultural Engineer, University of Kentucky

Wet weather this spring delayed corn and soybean planting in many areas and consequently pushed harvest later this summer.  Good drying conditions normally occur in September and October and will reduce operating costs for all drying systems.  Moreover, high temperature automatic batch and continuous flow dryers can be used to partially dry corn to 16 or 17 % moisture and unheated, natural air drying can be used to finish drying to the market level (normally 15.0%).  Drying limits for corn and soybeans are shown in Table 1 and 2, respectively.  These are the moisture levels each grain will reach after sufficient exposure to the air conditions shown.

Grain Storage and Drying Calculators

A lot of the grain harvested this fall was wet. Immediate sale of this grain resulted in dockage at the elevator. On-farm storage and artificial drying of the grain also has costs. Now that farmers have most of their grain out of the field, they can pay closer attention to how much on-farm storage is costing compared with the expected dockages at the elevators.

An excellent website on Grain Storage was has several calculators to help producers estimate the costs of drying grain, grain shrinkage, grain bin capacity, and related topics. Dr. Sam McNeill, Extension Agricultural Engineer, was the author of most of these calculators.

A related website for Proper Grain Storage and Handling includes additional relevant topics.