ď ą
seed is a LIVING ORGANISM It respires. During respiration, it consumes oxygen and generates carbon dioxide, water, and heat. It will ultimately die. Its lifespan depends on how it is being produced, processed and stored.
ď ą
seed is a HYGROSCOPIC PRODUCT
The seed is capable of absorbing water from or lose moisture to surrounding air Moisture content (MC) is used to describe the wetness or dryness of a seed Relative humidity (RH) is used to describe the wetness or dryness of the surrounding air
seed
Surrounding air is wet
When a dried (low MC) seed is placed in a humid environment (high RH), it has the tendency to absorb moisture from its surrounding air.
seed
Surrounding air is dry
When a wet seed (high MC) is placed in a dry environment (low RH), it has the tendency to lose moisture to its surrounding air.
Equilibrium MC of the seed exists when there is no more exchange in moisture between the seed and its environment. Equilibrium MC varies depending on the temperature and relative humidity of the surrounding
Equilibrium MC of rice at 25 C ambient temperature o
Relative Humidity (%)
Equilibrium MC (%) Palay
Milled rice
10
5.9
4.9
20
8.0
7.7
30
9.5
9.5
40
10.9
10.3
50
12.2
11.0
60
13.3
12.0
70
14.1
13.4
80
15.2
15.3
Viable The seed is alive and will germinate when sown under conditions favorable for germination.
Vigor The quality of the seed responsible for rapid and uniform field emergence, capable of performing well over a wide range of field conditions.
To maintain its quality, so that at its time of use, it will germinate and produce a healthy seedling. To ensure the availability of stock to meet the demand in any given year. To provide reserves for unpredicta ble conditions such as drought, flood, and war.
Storing seeds has its risks The risks can be high or low depending on the prevailing weather, the market requirements and the management provided during storage. The best alternative to avoid the risks associated with storing seeds is to avoid storing seeds as much as possible.
Storage parameters: Seed moisture content (MC) Temperature of surrounding air Relative humidity (RH) of surrounding air Of these three parameters, seed MC is the most important. RH ranks second because of its influence on seed MC. For ideal storage conditions (ex. cold storage), these three parameters have to be maintained as low as possible.
Storage duration Maintaining an ideal storage condition is costly and may not be practical especially on the part of the farmers or rice seed producers. A compromise may be done depending on the length of time the seeds have to be stored. If the seeds are to be used within 3 months, ambient storage may already be appropriate