Anchor Farm, Trent, Dorset
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Why Moisture Matters

Thursday 9th May 2013

Moisture in cropsMoisture content is critical from harvest, through storage, to final sale of cereals and oilseeds. If moisture is too high, there is a risk of quality reduction, or even crop loss in store. On the other hand, excessive drying is wasteful and can lead to reduced returns.

Balancing these opposing risks is not easy due to the variable nature of grains within a bulk and the inherent difficulties of measuring grain moisture accurately. Cereals and oilseeds which are too moist in storage can be subject to:

Mould-on-cropsGrain which is over-dried before, or during, storage can result in:

Grain moisture metering

Assessing moisture content on the farm

Grain moisture meters and probes, available for farm use, measure an electrical property related to moisture content, rather than grain moisture itself. Meters and probes rely on an inbuilt calibration between moisture and either electrical capacitance or resistance.

Meters and probes are calibrated against oven-based moisture determinations. All probes and capacitance meters use whole grain samples. Most resistance meters use a ground sample.

Meters are calibrated to operate most accurately within a specific moisture range, typically 11–20%. The accuracy of this method is +/- 0.5% at best.

Causes of variation:

Grain moisture samplingMeasuring moisture content in the laboratory

The most accurate method of measuring grain moisture content is the standard oven-based test, which uses an ISO-specified protocol to dry a prepared sample of ground grain in a special laboratory oven (ISO712). The weight lost during drying is used to calculate the moisture of the sample. The accuracy of this method is within 0.15%.

Causes of variation:

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