Seed processing is an important segment of the certification process wherein foreign material, inert matter undersized seed, weed seeds, off-size and deteriorated and damaged seeds are removed for upgrading the quality of seeds. The following procedures are involved after arrival of the seed produce to the seed processing units from the approved seed plots :
1. ACCEPTANCE OF BULK RAW SEED PRODUCE FOR PROCESSING
The official in charge of the seed-processing plant may, after verification of the relevant documents such as the final field inspection report, Form-1 and a letter of undertaking from concerned seed producer /grower to the effect that the seed produce has not been admixed/contaminated during harvesting, threshing, drying and transportation, accept the produce for processing subject to examination, verification of the following details:
Physical appearance of the seed lot with respect to lustre, inert matter content, etc
Infestation and damage caused by insects
Apparent infection by designated seed-borne diseases and presence of other crop seeds, objectionable weed seeds, other distinguishable varieties (O.D.V)
Moisture content of the seed
Total weight of the bulk seed in comparison to the expected yield as per final FIR.
The recommended screen aperture size should be used for processing of various seed crop varieties, (See Grading of Crop Seeds). The entire bulk seed produce as per estimated seed yield in the final field inspection report shall be accepted for processing. If the quantity of bulk seed surrendered for processing is abnormally more than the expected yield, recorded in the FIR the seed shall not be accepted for processing without the approval of the higher authority. The processing and sampling of all foundation and certified seed lots shall be taken up in the presence of the seed producer/grower. Processing and packing schedule as and when communicated by the Head Office of the Agency for each season should be strictly adhered to.
There are 114 registered seed processing units in the state regulated by the Agency. Out of this 39 units belong to the public sector and 75 belong to private seed-producing organisations.
2. CLEANING AND GRADING OF SEEDS
Pre-conditioning and pre-cleaning
The seed material to be processed should be properly conditioned and pre-cleaned by removing the seed appendages and particles such as trash, stones clods etc. which are larger in size than the desirable crop seed so as to increase the speed and efficiency of processing. This can be achieved by using pre-cleaning equipments like scalpers, debearders, huller-scarifier etc.
Basic seed cleaning
Pre-cleaned seed material is subjected for basic seed cleaning to remove the undesirable materials like trash, chaff, broken and damaged seed, undersized seed etc. besides uniform grading of seed based on seed size. Air screen cleaner is the most common equipment used for basic seed cleaning.
Principles of seed cleaning
Seed size and weight are the basic characters considered in the air screen cleaner for the separation of good seed from the undesirable materials in the bulk seeds. The basic principles involved here are :
Aspiration : The light seed and chaffy materials is removed from the seed mass through aspiration, i.e., lifting light material through air blast.
Scalping : The material which is larger than the required seed size like trash, clods, plant parts etc. are brought to a separate outlet where the good seeds are dropped down through the upper screen openings.
Grading : The uniform size grading of the cleaned seed material is achieved by retaining the seed and any other material larger than the required size on the top screen and by dropping down the small sized material through the screen aperture size of the bottom screen. Hence, the screen aperture size of the top screen will be more than the required seed size where as the screen aperture size of the bottom screen will be less than the required seed size. Thus the seed of the required size rolls over the bottom screen and is collected in a separate outlet.
Air Screen Cleaner
Irrespective of the model and make, all the air screen cleaners functions similarly with respect to scalping and grading. In a typical four screen cleaner, the first screen is for rough scalping, second screen is for rough grading, third screen is for close scalping and the fourth screen is for fine grading.
Screen aperture sizes are specified for each crop. However, Seed Certification Agency can permit the change of screen aperture sizes on specific necessity.
Tips for proper seed processing
Ensure proper pre-cleaning of bulk seed material before subjecting it for processing.
Check the moisture content of the seed material to be processed and take up drying if necessary.
Cleaning the seed bins, elevators, screens, seed cleaners and the gunny bags thoroughly before commencing seed processing.
Always use the recommended screen aperture sizes for processing of any crop seeds.
Do not process two variety seeds of the same crop one after the other. Change the crop or if it is inevitable, clean the entire processing system thoroughly before going in for the next variety of the same crop.
Check the quality of cleaned seeds periodically during processing by collecting samples at regular intervals and take up corrective measures if necessary. Similarly observe for the presence of good seeds if any in the rejected seed portion and take up immediate measures to adjust the feed rate, air blast etc. so as to prevent the loss of good seed material.
The ultimate aim of seed processing is to obtain uniform sized seed free from all undesirable material but at the same time to prevent the loss of any good seed as rejected material.
Maintenance of air screen cleaner
Check all nuts, bolts and screws daily and tighten or replace wherever necessary.
Check brushes and spring tension on brush drive mechanism regularly and adjust or replace them if necessary.