The Microwave Oven, Gram Scale Method

To determine hay moisture with the microwave oven and gram scale method, follow these steps:*

1. Collect samples from several locations in the field.
2. Mix the samples together and remove a sub-sample that weighs about 2 pounds.
3. Use sharp scissors or hedge shears to chop the sample into 1 or 1-1/2 inch lengths. Take care not to lose any leaves.
4. Accurately weigh out a sub-sample of about 100 grams.
5. Place an 8-ounce glass of water (3/4 full) in the back corner of the microwave. Keep the water amount somewhat constant during microwave use. This is as prescribed by microwave manufacturers.
6. Place hay in a donut shape on a moisture-free, paper plate. Then put it in a microwave oven for two minutes at half power.
7. After the two minutes are over, remove the sample, weigh it, and then return it to the oven for another minute of drying.
8. Continue this cycle of weighing and drying until the weight is not reduced more than 1 to 2 grams and/or forage begins to char. If any charring has occurred, use the previous weight for calculating the moisture content.
9. You are now ready to calculate the percentage of moisture by using this procedure:

Step One. Fill in the blanks.

First weight of sample _____________ (a)

Last weight of sample _____________ (b)

(Note: These weights should not include the weight of the plate. Therefore, subtract the weight of the plate before going any further.)

Step Two. Complete this equation.

b ÷ a x 100 = percentage of dry matter.

Step Three. Complete this equation.

100 - percentage of dry matter = percentage of moisture in the hay.

*It might be a good idea to follow this procedure twice. First, follow the procedure with samples taken from an average spot in the windrow. Then run through it again, this time with samples taken from the wettest spots. That way, you become aware of the average moisture, as well as problem spots.

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