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Microwaves Sense Grain Moisture

By Sharon Durham
December 31, 2001

A new technique that uses microwaves to determine moisture levels in grain crops has been developed by Agricultural Research Service scientists in Athens, Ga.

In the new process, an antenna transmits microwaves into grain such as corn, wheat, barley or soybeans. The microwaves pass through the grain and are received by another antenna. The microwaves' altering as they pass through spells out how much moisture is in the grain. The new procedure automatically adjusts for different types of grain.

ARS engineer Stuart O. Nelson, visiting scientist Samir Trabelsi and retired electronics engineer Andrzej Kraszewski developed the technique at the ARS Quality Assessment Research Unit in Athens.

Grain moisture is important because the level of water in grain is a key factor in determining when harvest should occur.

If harvesting occurs when moisture levels are too high, the combines can damage the grain in the threshing and shelling processes. If the moisture content is too low, there is the risk of damage from shattering and kernel breakage. Moisture information is also essential in determining whether grain can be safely stored without spoilage and in determining the selling price.

Using current technology, a separate calibration must be developed for each kind of grain, and corrections are required for differences in temperature of the grain and its bulk density. In many instances, samples must be collected and tested in handheld moisture testers or taken to grain elevators for more accurate testing. The new technique eliminates the need for multiple calibrations and compensates for grain density and temperature.

The new technique has potential application for use on combines and on grain handling or conveying equipment and provides for continuous moisture monitoring. Grain farmers and handlers could then have better information for managing their operations. If commercialized, the system is expected to be cost-effective because no other sensor is needed for density, and calibration maintenance is simpler.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.