“Pre-drying” is the stage of the post-harvest system during which the harvested product is dried in order to undergo the next operation of threshing, under the best possible conditions.
Why is pre-drying important?
At the time of harvesting, the cut portions of the plant may contain too much green plant matter and all the grains may not have reached a uniform degree of maturity and may have moisture content too high. This makes pre-drying essential.
How to pre-Dry
Pre-drying can be done in two ways
Type I Once maturity has been reached, allow the crop to pre-dry, standing in the field, before harvesting. But some inherent dangers are associated with this method of pre-drying. This may lead to :
shattering losses of grains
losses from attack by pests (rodents, birds, etc.)
losses from infestation (insects, moulds, etc.)
prolonged occupation of the field creats problems for using the land for a second crop
Type II Place the newly-harvested crop piles, in the field or on drying-floor. Prolonged exposure to the air (in sun or shade) reduces the moisture content of the grains to desired level. The shape and size of these piles can vary according to the crop to be pre-dried. However, following precautions must be taken :
Protecting the piles from sudden rains or nocturnal humidity and dew is essential in order to avoid repeated dampening of the shells and grains during pre-drying.
Direct contact of the grains with the ground must be avoided in order to cut down the risks of infestation (moulds, etc.).