Temperature Management in On-farm Grain Bins

Table 1. Recommended grain moisture content for safe storage.*

**Poor quality grain (broken, immature, pest damaged) should be held at 1% less moisture content than sound, high quality grain.

Table 2. Recommended grain temperatures for safe storage.*

***Be careful not to freeze grain of higher moisture contents.

*Source: University of Tennessee publication PB1724, "Maintaining Quality in On-farm Stored Grain."

Targeted percent grain moisture contents should be attained through a combination of one or several of the following: natural field maturation and drying, grain dryer, and bin drying using aeration fans.  The higher the percent moisture content of the grain coming out of the field, the greater the necessity to use heat producing dryer systems.   After grain is dried to an acceptable percent grain moisture content, it  needs to be cooled to the appropriate temperature for storage.  Aeration fans should be run shortly after the grain is removed from the dryer (after a steeping period of 4-6 hours or more) to begin cooling the grain.  Grain should be cooled in steps to the desired overwintering temperature.  Thereafter, aeration fans should be run when outdoor temperatures are 10-15 degrees F lower than the grain temperature. 

Aeration fan timing depends largely on the airflow (cubic feet per minute (cfm) per bushel) produced by the aeration fan(s) (see Table 3.).  It is recommended that air be pushed from the bottom to the top of the grain and the temperature of the grain be monitored in the headspace area to determine when the cooling/warming front reaches the top of the grain.  Once  desired grain temperature has been reached,  temperature should remain fairly stable in the grain mass because grain is an excellent insulator as long as there are no air movements through the grain mass.  Thus, after each aeration cycle is complete, the aeration fan should be blocked off to prevent unwanted air flows.

Table 3.  Estimated aeration cooling and warming cycles (hours).*

*Source: University of Tennessee publication PB1724, "Maintaining Quality in On-farm Stored Grain."

Grain management with fluctuating temperature, begins with checking the current temperature of the grain mass.  If the temperature is between the 30-40 degree F range, shut down the aeration fans, block off the opening of the aeration fan and monitor the condition of the grain regularly through the rest of the winter until the grain is moved to sell.  If the temperature is not yet in the range, continue running the fans to bring temperature down to the desired range.

Other tips for managing stored grain include:

1.  Be sure grain is level in the bin head space to assure even flow through the entire grain mass.  Peaked grain in the middle of the bin is usually problematic.

2.  Do not over-fill bins.  Access to the head space area is nearly impossible when a bin is over-filled.

3.  Be safe in working in and around grain bins.  Work in teams, have safety plans, use lock-out to prevent augers from being started when one is working inside of a bin, and never enter a bin that is being loaded or unloaded.

4.  Monitor your grain through the winter on regular basis.