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Farm Management
First Posted Mar 18, 2008
Jul 22, 2010

Determine Hay Moisture and Spontaneous Combustions Levels

Have you ever considered the amount of moisture content in your hay and the negative effects of too much moisture? There are many causes of barn fires with wet hay topping the list. Wet hay can facilitate spontaneous combustion. Also, moldy hay, often caused by too much moisture content in the hay, can cause a horse to colic.

    What Can Cause Barn Fires?

  • Wet hay
  • Lightning
  • Smoking
  • Extension cords
  • Heaters and electrical appliances
  • Dust/Clutter
  • Outdated and improper construction
  • The presence of accelerants - gasoline, oil, kerosene, aerosol cans and others
  • Hay and straw storage
  • Running motors such as a tractor
  • Frayed electrical wires
  • Rodents chewing electrical wires

The following is a breakdown of what the parameters are for moisture content in your hay:

    Moisture Suggestions for Storing Hay
    Prepared by Donald K. Myers, Extension Agronomist Emeritus

  • Baling hay - 20% or less
  • Large bales or stacks - 17% or less
  • Upright silo (open) - 60-65%
  • Sealed silo - 50%
  • Horizontal or bunker silo - 65-70%

How Do You Determine Moisture Content In Your Hay?

There are a number of methods that can be used to determine the amount of moisture content in your hay. One is the use of a microwave. How To Determine Moisture Content In Hay

How Do You Determine When Your Hay Might Combust?

"A simple probe inserted into a haystack can accurately monitor temperature. You can make the probe with a 10-foot piece of pipe or electrical tubing. Sharpen the pipe or screw a pointed dowel to the end. Then drill several one-quarter inch diameter holes in the tube just above the pointed end. Drive the probe into the haystack and lower a thermometer on a string into the probe. The thermometer should be left for 10 minutes in several areas to ensure an accurate reading. Watch for these temperatures within your stack:

  • 150 degrees- Point of center. Check temperatures daily.
  • 160 degrees- Danger zone. Measure temperature every four hours and inspect the stack.
  • 175 degrees- Very flammable. Call the fire department. Wet hay down and dismantle the stack.
  • 185 degrees- Expect hot spots. Flames will likely develop when heating hay comes in contact with air.
  • 212 degrees- Temperature rises rapidly. Hay will most certainly ignite. Fight and contain fire."
August 3, 2000 issue of Agri-View

John Markus
Area Agricultural Agent

Farm Management