UK Calculator for Stored Grain Capacity, Bin Sub-floor Volume and Wall Area

As corn and soybean harvests approach, stored grain managers on farms, elevators and warehouses are preparing different types of structures for service. This may include applying approved insecticides or grain protectants to guard against damage caused by insects during storage.

The recommended rate for most stored product protectants is based on either the volume of grain (bushels) or void space (cubic feet), or surface area of the grain or structure (square feet) to be treated.

The UK storage volume calculator has always included tables that show the capacity (in bushels) of conventional round bins, horizontal storage structures (such as machinery sheds and warehouses), large round piles/rings, grain bags and corn cribs. It now includes a new worksheet to calculate the surface area of bin walls and grain piles, as well as the volume of the space below perforated floors and air space above the grain surface.

Download Storage Capacity Spreadsheet    Download Corn Harvest Lost PDF

2022 Decision Tool Updates for Grains

Equilibrium Moisture Content for Grains

Moisture exchange between grain and the surrounding air is driven by differences in vapor pressure. An equilibrium state is reached when there is no net exchange of water vapor between the grain and air. This has important implications in grain drying and storage systems. As air is warmed, the relative humidity is reduced along with grain moisture (drying process). When dry grain is placed in storage and cooled, grain moisture remains constant and the relative humidity of the air surrounding it is lower.

Equilibrium moisture properties have been determined for different grains and are reported as a Standard by the American Society of Agricultural and Biological Engineers. In general, mold growth is suppressed during storage when the environment is maintained at a relative humidity level of 65% or lower, and insects are suppressed at temperatures below 60 F.

Implications for drying

Grain will reach the moisture levels shown in the tables when exposed to the corresponding temperature and humidity levels for a sufficient period of time, which depends primarily on temperature and airflow. This can occur in the field or a bin. In a bin, drying time will depend on the airflow rate through grain, which in turn depends on the depth of grain. 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

The stagnant air space between grain kernels in a bin or bag will have the humidity indicated at the corresponding moisture and temperature. For example, 15% corn at 60 degrees will generate a relative humidity in the air space between kernels of 70%, but when cooled to 45 degrees will have a relative humidity of 65% (Table 1). Similar data for soybean, soft red winter wheat and grain sorghum (milo) are shown in Tables 2-4, respectively. Additionally, a new calculator is available for 12 other grains and oilseeds that are grown in Kentucky, as shown in Table 5.