Growing Food: A Guide to Food Production

O Storage

The two critical factors for the safe storage of seed, and food, are temperature and
relative humidity. Food also requires carefully controlled storage conditions, but even
greater care is needed with seed because it is a live product that needs to be kept in
certain specific conditions if it is to maintain its germination and vigour.
If the quality (germination rate and vigour) of seed is to be maintained for a long
period of time, there is a useful guide:

Relative humidity (%) + Temperature ( °F ) = 100 or less

This means, in theory at least, that in hot regions the relative humidity of the air should
be reduced, and in humid regions the storage temperature should be reduced.
However, irrespective of the climate and storage conditions, the higher the average
temperature, the lower the moisture content of the stored seed should be.

In practice it is usually difficult to adjust either the temperature or the relative humidity,
so it can sometimes be a good idea to transport the seed to a cooler, drier place if it has
to be stored for a long time.
All seed benefits and remains viable for longer periods if it is stored cool and dry.
However the specific requirements for each crop can be very different, and the viability
of seed depends on many other factors in addition to temperature, relative humidity and

In general seed should not be stored for more than a few days if the seed moisture
content is more than about 13%. In humid or very hot climates, 9–10% is advisable,
while in cool, temperate climates seed can be stored safely for several months at up to
16–17%.
Metabolic activity in grain practically ceases below about 8% moisture.

Measurement of Seed Moisture Content
The moisture content of grain can be easily and quickly measured by using small hand-
held meters. These meters can be used in the field if necessary, and measure to within
0.1% accuracy. They are operated either by batteries and/or mains/solar electricity.
Moisture meters measure either the electric conductivity or the dielectric constant of
the sample. The moisture content is shown instantly on the meter, and is quite accurate
enough for most field work. Even more accurate measurements can be made in a
laboratory, but are rarely needed.

100 TONY WINCH

1. Seed Moisture Content

seed moisture content, as discussed in 1Fa. “Germination”, page 46.