Seed preservation starts from seed production. The seed preservation process comes to an end with sowing transplanting in the field.
Seed preservation includes all the operations properly done for seed production, drying, processing, quality control, and marketing. Conditions for seed preservation are given below,
The following points should be kept in mind for seed production:
- Crop cultivation is only for seed production.
- Not to cultivate the same crop near the selected land.
- Collection of seed from a reliable organization for seed production.
- Removal of crop plants of other varieties during seedling growth.
- Frequent field inspection of seed crop for (A) controlling weed (B) removal of other varieties from croplands (C) taking appropriate measures to control insect pests and diseases.
- Keep care to crop maturity.
- Cleanliness in crop harvesting, threshing, and winnowing.
Seed drying is required for higher seed longevity and for controlling insect infestation. There is no alternative to seed drying to increase seed viability and seed germination. Actually, the seed is dried to bring the seed moisture content to a standard level. At the time of harvest, seed moisture content remains 18% to 40%. This moisture level deteriorates seed viability. For that reason, to use this seed in the next season, it is essential to lower seed moisture content at 12% or below. So seed drying is necessary.
Methods of seed drying
There are two types of seed drying. These are:
(1) a) seed drying in the natural or normal air b) seed drying by enforcing natural air and
(2) seed drying by enforcing heated air in the seed container.
If the moisture content of the surrounding air is higher than that of the seed, the moisture from the air moves towards the seed until moisture equilibrium exists. It is necessary to keep the surrounding air dry To keep seed moisture at a safe level.
Duration of seed drying depends on (1) seed moisture content, (2) air temperature and humidity, (3) velocity of air, and (4) amount of seed.
It should be kept in mind that (1) drying of seed at very high temperature is harmful to seed. For example, decrease seed viability and seed germination.
(2) this type of injury may occur if the seed is drying at a lower temperature.
If the seed is dried at the appropriate temperature-
- High-quality seed is available.
- Seed is preserved for a longer duration.
- Possibility of higher economic benefit from seed business.
Seed processing may be defined as all the operations done for seed separation after harvesting and maintaining seed quality and germinating ability until the next sowing. The important activities for seed processing are dividing seed according to seed size and taking measures for preservation. The facilities achieved by proper processing-
- Increase seed purity;
- Looks attractive;
- Increase germination capacity.
Seed quality control
Seed quality control means the production and processing of seed to ensure quality seed which includes seed production by applying
appropriate agronomic practices, crop harvesting, threshing, and winnowing properly, bringing safe moisture levels by appropriate drying method, etc. In all the activities, there is a scope to control seed quality.
The following activities are essential to control seed quality:
There are (1) pure seed, (2) weed seed, (3) other crop seed (4) inert matter (stones, etc.) present in a seed sample. Among these four components, the determination of the percentage of pure seed is known as the purity test.
Seed germination test
How many seeds in a seed sample are germinated on a percentage basis is determined by a test. This test is known as the seed germination test. Germination starts when seed moisture content exists 35-60% or above. It is expressed in percentage terms. 100 seeds are calculated, and these seeds are then kept in a pot containing sandy soil, and water is applied to it to keep it wet. Every day it is observed so that the water is not empty. After a certain period, seed germination will be started. The number of seeds germinated is the rate of seed germination.
Seed moisture test
The method of determining the amount of moisture present in the seed by removing moisture from the seed is known as the seed moisture test. It is expressed in a percent basis by the following formula:
Seed vigor test
An unfavorable condition to seed germination is created for this test. It is considered that which seed will germinate much in this condition will be of higher seed vigor.
Seed marketing is a remarkable part of seed technology. Seed collection, packaging, seed preservation before the sale, notification, selling, etc., are combinedly known as seed marketing.
The following information is to be given to the customers during seed marketing:
- Variety of seed
- Amount of seed
- Certified seed or not
- Seed germination percentage
- Seed purity percentage
- Seed moisture content
- Seed longevity
- Name of the seed grower/ organization
- Name of the seed certification agency
- Seed marketing system
- Instructions on seed preservation
- Seed price
Importance of seed preservation
Seeds are susceptible. A minimum carelessness can deteriorate the quality of a large amount of seed. Farmers preserve seeds following their own experience. Although only the objective of seed preservation is to sell healthy and vigorous seeds in the next season, there are different seed preservation methods to keep care not to deteriorate seed viability. Seeds deteriorate during the period of harvesting, threshing, and transportation. Ten percent of crops are damaged by rats, birds, fungi, moisture, etc. Besides dust, dirt and concrete, etc., remaining in seed also deteriorates seed quality.
The main objectives of seed preservation are to maintain seed quality and carefully prevent the factors that hamper the seeds.
Methods of seed preservation
There are several methods of seed preservation in Bangladesh. Different seeds require different methods of preservation. Such cereal crops as rice, wheat, and maize are preserved in barns, earthen pots, gunny bags, poly bags, and beds. The methods of seed preservation are discussed below:
Seed drying and preserving in gunny bags
Seed drying means the removal of excess moisture from the seed and bringing it to a safe level. It is better if the moisture level is 12-13%. In Bangladesh, the seed is dried in the sunshine. Seeds must be dried for three days in high-intensity sunlight to bring this moisture to 12-13%. The seeds are being tested by biting to ensure proper drying. If the bite creates the ‘crunch’ sound, it ensures the proper drying. After that, the seeds are kept in the gunny bags and closed the openings, which are kept in the storehouse. The neem leaves, neem roots, dust of apple seeds, etc., are mixed with the seeds bags to save the seeds from insect attack.
Preserving rice in a barn
Rice gola is used To preserve rice. The size of the rice gola is constructed depending on the amount of seed. Before keeping seeds, a layer is made of cow dung and soil on the inner and outer layer of the goal and makes it suitable for preserving seeds. The seeds should be kept in the gola so that the gola becomes airtight. For that reason, by closing the opening of the gola, a layer is made by cow dung and soil on the opening of the ice gola.
Preservation in dol (large hollow basket made of bamboo slips) Dol is smaller than rice granary in size. It is round in shape and made of bamboo or wood. Like rice gola, inner and cuter side of the dol is coated with the mixture of cow dung and soil, and it is made suitable for preserving seed after drying well.
Preservation in a polythene bag
Nowadays, seeds can be preserved in a polythene bag of 5 kg capacity. The bag was invented by RDRS. Polythene for keeping seed is thicker than normal polythene. Dry seed should be kept in a polythene bag so that no space is available in the bag and. The air is totally removed out from the bag. After that, the bag opening should be sealed by applying heat so that there is no scope for entering air into the bag from outside.
Preservation in Motka (earthenware jar)
Motka is a soil-made round pot. It is most popular in rural areas. It is very thick and very durable. Coating of soil or tar is applied on the outside of Moika. Dry seed should be fully filled up in the motka and placed in a specific slat area in a granary. After that, a lid is to be placed for covering motka and sealed with coating. Fig: Seed preservation in motka