Storage of seeds is essential for saving the seed for next season. If stored properly, seed may useful for more than year.
As seed is stored for a year or sometimes more than one year, it is necessary to understand how harvesting practices, processing and seed storage affect the longevity (long life) and vigor (Physical strength and good health) of seed.
Proper harvesting time is that when seeds are matured on plant as long as possible without becoming fruit diseased. Seed harvesting can be done either by dry processing or wet processing.
In dry processing, already matured and dried seeds are harvested from seedbearing part of plant. Beans, okra, sunflower etc are examples of dry processing.
On the other hand, wet processing is followed when matured seeds are found inside of fleshy fruit/ berry. Cucumbers, tomatoes, melons etc are examples of wet processed seed.
After harvesting and air drying, seeds are threshed to separate from surrounding plant part. Sometimes, seed pods may split during drying. Seeds then should be stored in a well ventilated and low humidity area.
Moisture content of seed, humidity of storage place may affect seed quality (germination percentage, logevity, viability etc). Longevity of seed is increased as temperature decreases during storage of seeds. This applies for majority of seeds. If seed moisture is increased, longevity decreases.
(Source: SEED PROCESSING AND STORAGE Principles and practices of seed harvesting, processing, and storage: an organic seed production manual for seed growers in the Mid-Atlantic and Southern U.S. By Jeffrey H. McCormack (2004). Available at https://www.carolinafarmstewards.org/wp-content/uploads/2012/05/SeedProcessingandStorageVer_1pt3.pdf
For more detail, click on below link to visit ICAR e course lecture (Lesson 41: Storage of seed) http://ecoursesonline.iasri.res.in/mod/page/view.php?id=924