SEED PROCESSING

Seed lots received from the field are often at high moisture content and contain trash and other inert material, weed seeds, deteriorated and damaged seeds, off-size seeds, etc. Seed processing is necessary in order to dry the seeds to safe moisture level; remove or reduce to the extent possible the various undesirable material, weed seeds, other crop seeds, deteriorated or damaged seeds; uniform size grading and seed treatment to upgrade the overall seed quality.
Seed processing refers to all the steps necessary for preparation of harvested seed for marketing, namely, handling, drying, shelling, preconditioning, cleaning, size grading, treating and packaging etc.Drying- In order to facilitate processing, to prevent losses in germination and to reduce the chances of insect attacks during storage, seeds must be dried to an appropriate level. Drying generally involves the removal of moisture distributed inside the whole seed.
Sun drying / natural drying: Natural drying is done by spreading the seeds on trays, floors or fields on the open sun. The main advantage of this method is that it requires no additional expenditure. The disadvantages are delayed harvests, risks of weather damage and mechanical mixtures.
Artificial drying: Involves passing of heated or unheated air through the seeds to remove moisture. In unheated drying air should have low relative humidity hence it is not effective in moist weather. Heated drying is quicker, faster and requires less drying space but the disadvantages are high initial costs, damage of fire and possibility of overheating the seed.
The seed from threshing floor is mixed with seeds of other crops and of weed seeds, pieces of straw, gravel, soil etc. In the cleaning process the separation of undesirable material from desirable material is done on the basis of differences in physical properties. The principle differences found in seeds are seed size, density, shape, surface texture, colour, etc.
Different machines are available to separate seeds from inert matter. For e.g. specific gravity separator divides seed on the basis of weight and size, pneumatic separator separates seeds on the basis of there resistant to overflow, spiral separator separates them on the basis of seeds shape.etc
Grading: is the removal of smaller and shrivelled seeds from the well field healthy seeds. In India, air and screen machine is extensively used for cleaning and grading purpose.