Introduction
Seed has been an important agricultural commodity since the first crop plant
was domesticated by pre-historic man. For thousand of years, man cleaned
seed of his food crops by winnowing. This is still an important process, but it is
no longer adequate to supply the kind of seed needed by farmer.
Seed processing is a vital part of the seed production needed to move the
improved genetic materials of the plant breeder into commercial channels
for feeding the rapidly expanding world population. The farmer must get the
quality seed that is free from all undesired materials because farmer’s entire
crop depends on it.
Seed can seldom be planted in the condition in which it comes from the
growers. In fact, many seed lots contain weed or crop seed or inert material
that make them unfit for sale without processing. Crop seed also frequently
have stems, awns, clusters or other structures, which prevent from flowing
through the drill freely.
Seed processing is that segment of the seed industry responsible for
upgrading seed (Fig. 1), improving planting condition of seed, and applying
chemical protectants to the seed.
Advantages of seed processing:
1. Make possible more uniform planting rates by proper sizing
2. Improve seed marketing by improving seed quality
3. Prevent spread of weed seed
4. Prevent crops from disease by applying chemical protectants
5. Reduces seed losses by drying
6. Facilitate uniform marketing by providing storage from harvest time until
the seed is needed for planting.
An important factor to consider is the moisture content of the seed prior to
processing. Seed with moisture content above 15% are subject to excessive
damage in the processing line. In this case natural or artificial drying may be
necessary.
Physical characteristics used to separate seed include size, length, weight,
shape, surface texture, colour, affinity for liquids and electrical conductivity.
Seed processing can broadly be divided...