How to Test Weight & Moisture Content With a Grain Sample

Moisture can affect the market value of grains.

The issue of moisture is of profound importance in the growing, storage, selling and purchase of grain. Affecting weight, volume and the preservation of nutrients, moisture is a factor in most grain-related transactions. Farmers and grain buyers -- and their attorneys -- write contracts specifying allowable moisture content as well as acceptable conditions and durations for holding grain before its transfer. To this end, all parties must be in accord with regard to wet matter/dry matter weight ratios. The procedure for arriving at these figures should also be agreed upon. A very common method in use is heat-oven drying.

Things You'll Need

• Grain scale
• Grain divider
• Grain dryer

Instructions

1. Obtain a representative grain sample. Take grain in equal measure from each storage bin and from random locations within each bin. Use a dipping scoop or suction hose for best results, but hand retrieval is also acceptable.

2. Mix the aggregate of the retrieved portions completely. Use a grain divider to apportion the aggregate into sizes practical for your scale. Optimal sizes vary by grain and purpose, but 500 to 1,000 grams is normally effective for moisture testing.

3. Place the first sample on the grain scale. Calibrate the device to account for the grain container by placing the empty vessel on the scale first to get an accurate reading. Some scales have auto-calibration, which will then discount the container weight for subsequent weight measurements until reset. Wait for a settled digital reading before recording the weight. Repeat for each sample.

4. Place the total sample in a continuous flow dryer for best air flow. Set the dryer fans for the moisture content best for the storage health of the grain. For example, storing corn at 15 to 18 percent moisture will require drying at two cubic feet per minute per bushel.

5. Weigh the dried grain on the same grain scale as before. Subtract the dry weight from the wet weight, dividing the difference by the wet weight. Multiply this quotient by 100 to arrive at the percentage of moisture in the original samples.

Tips & Warnings

• Take caution when operating a grain dryer. Follow operator instructions meticulously.

References

• North Dakota State University Agriculture and University Extension; Grain Moisture Content Effects and Management; Kenneth J. Hellevang; 3/1995
• University of California -- Davis Plant Sciences Dept.; 2003 Rice Quality Workshop; Measurement of Grain Moisture
• Penton Media, Inc.: "Farm Industry News"; Sizing Up Grain Dryers; Jodie Wehrspann; 5/1/1998
• Ontario Corn Producers Association; Grading Corn; Jim Lowe
• USDA Grain Inspection, Packers and Stockyards Administration; Technical Services Division; Grain Sampling Procedures
• Hornady Manufacturing; Hornady Electronic Scale, Model GS-350; Instruction Manual

Resources

• U.S. Grains Council
• North Dakota State U. Agriculture and University Ext.; Grain Drying; Kenneth Hellevang; 11/1994
• University of Arkansas Extension; On Farm Storage and Drying; Dennis Gardisser