Bradbrook - 2012 - Rice Farming complete with methods to increase ric

quality of the milled rice are greatly improved. Cleaning can be done manually or
mechanically.
a. Winnowing
In winnowing, the grains are placed on a winnowing tray which is then manually
shifted in a to-and-fro or up-and-down movement against a blower, air fan or the
wind. This method of cleaning will remove lighter materials such as bits of straw,
weed seeds, chaff, and unfilled grains. However, heavier materials such as dirt,
stones, off-types, and other weed seeds remain with the grain. This type of
cleaning is both labor intensive and time consuming.
A hand-operated wirmower can hasten the cleaning process and handle a greater
volume of grains. The grains are placed on a tray at the top of the winnower, then
it is shifted down an inclined air duct using a hand-cranked wheel. A blower at the
bottom of the tray blows away the lighter material as the grains fall down the air
duct to a catchment tray at the bottom of the setup.
b. Screening/sifting
This machine has several layers of sieves of different sizes. The threshed grains
are placed at the topmost layer and the machine shakes to sift the grains through
each layer of sieve until only the rice grains are left. This method of cleaning can
handle large volumes of grains in a relatively short period of time compared with
manual or hand-operated cleaning.
c. Seed cleaner
This machine is a combination winnower and sifter. A fan removes lighter
impurities in the harvested grains, then a sifter removes the heavier impurities.
Cleaned seeds should be inspected prior to storage. Consider removing those that have
malformations or discolorations, those that have germinated, or those that are broken
or moldy. Such seeds can greatly impact the quality of the seed, its viability and vigor.
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