📈 Seed Processing and Storage

This lesson builds core elective concepts in BSc Agriculture with practical applications and exam-oriented clarity.

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Seed Processing and Storage

Seed processing involves all operations performed on harvested seed lots to improve their quality, purity, and marketability. Seed storage maintains seed viability and vigor until the next sowing season.

Seed Processing Steps

1. Pre-cleaning

• Removal of large impurities — straw, leaves, stones, clods
• Equipment: scalper or air-screen pre-cleaner

2. Drying

• Reduce seed moisture to safe storage levels
• Target moisture content varies by crop:

Crop	Safe Moisture (%)
Rice	12-13
Wheat	12
Maize	12
Groundnut	8-9
Vegetables	6-8
Soybean	10-12

• Sun drying — spread seeds in thin layers on clean threshing floors
• Mechanical drying — using heated air dryers (temperature not exceeding 40-43 C for most seeds)

3. Cleaning and Grading

• Separation based on size, shape, weight, and surface texture

Equipment	Separation Basis
Air-screen cleaner	Size (screens) and weight (air blast)
Indent cylinder/disc	Seed length
Gravity separator	Specific gravity/density
Spiral separator	Shape (round vs flat)
Magnetic separator	Surface texture (using iron powder coating)

4. Seed Treatment

• Fungicide treatment — Thiram, Carboxin + Thiram, Carbendazim for seed-borne pathogens
• Insecticide treatment — Imidacloprid, Chlorpyrifos for stored grain pests and early seedling pests
• Bioagent treatment — Trichoderma viride, Pseudomonas fluorescens
• Polymer coating — modern technique providing uniform application and visual identity

5. Packaging

• Seeds packed in moisture-proof bags (polythene-lined or laminated)
• Standard pack sizes: 1 kg, 2 kg, 5 kg, 10 kg, and 25 kg depending on crop
• Each package must carry the seed label (tag) with certified information

Seed Labeling

The seed label must include:

• Crop and variety name
• Lot number and class of seed (breeder, foundation, certified, TL)
• Date of test and test results (germination %, purity %, moisture %)
• Net weight
• Name and address of the producer/seller
• Expiry date (validity period)

Seed Storage

Principles of Seed Storage

The Harrington Rule states:

• For every 1% decrease in seed moisture, storage life is doubled (within 5-14% moisture range)
• For every 5 C decrease in storage temperature, storage life is doubled (within 0-50 C range)

Storage Types

Type	Conditions	Duration
Open/ambient storage	Normal temperature and humidity	6-9 months
Dehumidified storage	Controlled humidity (< 40% RH)	12-18 months
Cold storage	10-15 C, 40-50% RH	2-5 years
Cryopreservation	-196 C (liquid nitrogen)	Decades (gene banks)

Storage Pests and Management

• Rice weevil (Sitophilus oryzae), Lesser grain borer (Rhyzopertha dominica), Pulse beetle (Callosobruchus spp.)
• Control: Aluminium phosphide fumigation, deltamethrin dusting, hermetic storage (triple-layer bags)

Proper seed processing and storage are essential links in the seed value chain, ensuring that high-quality seeds reach farmers with optimum germination and vigor.

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Summary Cheat Sheet

Topic	Key takeaway
Main focus	Seed Processing and Storage — cleaning, grading, drying, treatment, packaging, and storage conditions for maintaining seed viability.
Section context	Revise this lesson with the rest of Post-Production Management for stronger conceptual continuity.