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OSU Extension

College of Food, Agricultural, and Environmental Sciences

May 24, 2016 - 4:13pm -- lewandowski.11@...

          A lot of cereal rye and hay fields have been mowed in the past week to 10 days and harvested as wrapped baleage or as silage.  A critical component to getting good fermentation on these forage products is baling or chopping for ensiling at the right moisture content.  Although there are a number of products on the market that can provide a moisture reading purchasing a used or second-hand microwave could prove to be one of the better business decisions because it is a reliable tool to determine forage moisture.   A recent issue of the OSU Extension Beef Cattle Letter included the following instructions regarding the microwave method to determine forage moisture content.

         Although this method takes about 20 minutes to complete, the measured moisture concentration is much more accurate than those from electronic conductance moisture testers, especially for high moisture sample like silage and baleage.

Before using the microwave oven method, obtain the following items:

  • Microwave oven
  • Scale (must weigh in grams)
  • Microwave-safe plate
  • 10- to 12-ounce cup of water (a coffee mug works best)
  • Pencil and paper

Use the following procedure for the best results:

  1. Obtain a representative forage sample (whole plant material).
  2. Cut the sample into 1-inch pieces; keep leaves and stems uniformly mixed.
  3. Weigh the plate and record it as “plate weight.” This will be subtracted during the final calculation.
  4. Add approximately 100 grams of the forage sample to the plate; spread the sample as uniformly as possible.
  5. Weigh the plate with the forage sample and record it as “initial weight.”
  6. Place the cup of water in the corner of the oven to capture unabsorbed microwaves as the plant tissue dries. This prevents sample from igniting.
  7. Place the sample on the plate in the center of the oven.
  8. Set the oven on HIGH for 2 minutes and “cook” the sample.
  9. Remove the sample and plate, weigh them, and record the weight.
  10. Change the water in the cup to prevent the water from boiling over.
  11. Set the oven on HIGH for 45 seconds to 1 minute and “recook” the sample.
  12. Remove the sample and plate, weigh them, and record the weight.
  13. Repeat steps 7 through 10 until the weight does not change more than 1 gram (this means the sample is dry); record as “final weight.”  As you get near the end of this process you may be microwaving the sample for no more than 30 seconds.  You must avoid charring the sample.
  14. Use the following equation to determine the percent of moisture of the forage sample:

Percent moisture (%) = (Initial weight – Final weight) x 100 divided by (Initial weight – the Plate weight)