Storage

The main objective of seed storage is to maintain high seed germination and vigour from harvest until planting.

 

Stages of Storage

The seeds are considered to be in storage from the moment they reach physiological maturity until they germinate. Thus, the entire storage period can be divided as follows: -

·         Storage on plants (physiological maturity until harvest)

·         Harvest, until processed and stored in warehouse.

·         In storages or warehouses.

·         In transit.

·         In retail stores.

·         On the users’ farm.

 

General Principles and Measures

·         Seed storage conditions should be dry and cool.

·         Effective control on storage pests is to be maintained.

·         Proper ventilation, high plinth, sanitation, free from leaks and dampness besides being rodent and bird proofing in seed stores are the prerequisites.

·         Before placing seeds in storage, they should be dried to safe moisture levels appropriate for the storage system.

 

Seed Moisture Content and Seed Storability

The role of moisture in the life of a seed is as follows: 

Seed Moisture Content

Effect on Seed

35-80%

Moisture content of developing seed, seed not mature enough for harvest.

18-40%

Seed physiologically mature; respiratory rate high; seed susceptible to field deterioration; heating occurs if seed bulked without adequate ventilation; molds and insects very active; seed susceptible to mechanical damage in harvesting and handling.

13-18%

Respiratory rate still high; can get heating at higher levels; molds and insects can be damaging; seed resistant to mechanical damage.

10-13%

Seed store reasonable well for 6 to 18 months in open storage in temperate climates; insects can still be a problem in susceptible seed; seed susceptible to mechanical damage.

8-10%

Seed sufficiently dry for 1 to 3 years open storage in temperate climates; very little insect activity; seed very sus­ceptible to mechanical damage.

4-8%

Safe moisture content for sealed storage.

0-4%

Extreme desiccation can be damaging to seed; hardness develops in some kinds of seed.

33-60%

Seed germinate when they imbibe water to these levels.

 

The rate of deterioration of crop seed in storage increases as seed moisture content increases.

Mature seed are hygroscopic. Their moisture content will vary with the relative humidity of the atmosphere, although not as quickly as changes occur in atmospheric relative humidity. Mois­ture absorption or description of seed is a relatively slow proc­ess.

Equilibrium moisture content varies among different kinds of seed. In general, the equilibrium moisture content of oil seed is lower than that of starchy seed at the same relative humidity and temperature.

While both seed moisture content and temperature are important factors in seed storage, moisture content has greater direct influence on seed longevity. Very dry seed will store well at temperatures up to 90o F.

Good storage conditions are achieved when percent relative humid­ity plus storage temperature in degrees Fahrenheit add up to no more than 100. However,

A ONE (1) PERCENT DECREASE IN MOISTURE CONTENT NEARLY DOUBLES STORAGE POTENTIAL OF SEED; and

A TEN (10) DEGREE DECREASE IN TEMPERATURE NEARLY DOUBLES STORAGE POTENTIAL OF SEED.

·         Only high-quality seeds are to be stored i.e. well cleaned, treated as well as of high germination with vigour and good pre storage history.

·         Before arrival of new produce, all processing and storage structures should be thoroughly cleaned and disinfected with residual sprays of insecticide such as malathion 50EC (one part in 25 parts of water) along with seed containers to kill hidden insects.

·         Seeds should be pre cleaned and its moisture content be reduced below 9% preferably.

·         Generally, the insect infestation starts when seeds are kept in pre-processing sheds. To prevent this, fumigation with aluminum phosphide @ 2 tablets of 3 gm. each per ton with an exposure period of 3-5 days is necessary, but the moisture percent of the seed to be fumigated should not be more than 12%.

·         Processed seed may be treated in the order of fungicide ¦ insecticide   ¦ rhizobium culture.

·         In generally processed seed may be treated with Carbendazim 50% WP@ 3 gm. per kg. seed.

·         Processed seeds should be stored and stacked properly and must not be kept in an area where unprocessed or carry over seeds are kept.

·         The seed package, in reality is a small storage container. The kind of container needed is affected by several factors like, quantity of seed desired in each pack, protection desired, cost of the package, value of the seed, storage condition and facili­ties for drying the seed. As a matter of convenience to the farmer and looking to the small land holdings the package is often designed to hold seed to plant one acre or one hectare.

·         The temperature is one of the most important environmental factors which influence seed viability and vigour during storage. The lower the temperature, the longer will be the maintenance of germination capacity. Thus, temperature should be controlled either by ventilation, insulation or by refrigeration.

·         To eliminate convection transfer of moisture, an operating exhaust fan be used to break the convection current. To prevent moisture transfer through floor, the floor should be three feet above the ground level with sand and/or rock filled with moisture proof barrier under the concrete.

 

Stacking

For stacking of the seed RSSOCA has issued general instructions which are: -

·         Seed bags should be stored properly i.e. crop, variety, and stage wise on the wooden or CR steel pallets/crates with proper matting/tarpaulin and sufficient space in between two stacks. 

·         All the stacks of seed bags should be properly layout leaving sufficient space in between each stack for free movement and should be kept away from the walls so that the stacks are accessible for inspection, fumigation etc.

·         Seeds especially that of Soybean etc. is prone to stack pressure and may lose their germinability if the pressure is more than desirable. Precaution should be taken to avoid higher stacks i.e. not more then 8-10 bags.

·         Crops like Wheat, Gram, Barley, Guar, Moong, Moth, Arhar can withstand a greater load and the stacks in such cases can be raised to a height of 15 to 18 bags but not allowed more than 18 bags. (bag wt. 60 kg)

·         Use of hooks in bags, carrying cloth bags should always be avoided while handling stocks.

·         Stack cards should invariably be used to show the details of lots stacked and fumigation operations etc.