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Vacuum Sealing vs. Refrigeration: Which is the most effective way to store seeds?
By: Marcia Croft, ECHO Asia Impact Center Volunteer, Mae Ai, Thailand; Abram Bicksler, Director of Sustainability Research and Instructor, ISDSI, Chiang Mai, Thailand; James Manson, ECHO Asia Impact Center Volunteer, Mae Ai, Thailand; Rick Burnette, Director, ECHO Asia Impact Center, Chiang Mai, Thailand
Storing seeds in the tropics can often be difficult; with high temperatures and humid conditions, seeds lose their ability to germinate quickly. Many techniques for seed storage exist, from the high-tech standards of gene banks to simple methods used by villagers for saving their own seeds. All have their strengths and weaknesses, but when balancing costs and resources, which methods are really the most effective? To find appropriate low-input storage methods for storing seeds, the ECHO Asia Seed Bank recently completed a study on tropical seed storage under the resource-constrained settings this seed bank encounters.
The three key factors that determine the rate of seed deterioration in storage are: oxygen pressure (amount of oxygen with the seeds in storage), seed moisture content, and temperature (Roberts, 1973). An increase in any of these factors will lower the storage life of the seeds, and as a general rule any increase of 1% moisture content or 10o F (5.6o C ) in storage will halve the storage life of the seeds (Bewley and Black, 1985). Each factor contributes to seed decay in specific ways, and minimizing these conditions is critical to effective seed storage.
The goal of this research was to evaluate two seed storage options: vacuum sealing and refrigeration. Vacuum sealing is a relatively low-cost method that requires few inputs after an initial investment. Sealing helps conserve seed quality by minimizing oxygen presence and exposure to ambient humidity, thereby keeping seed moisture content low. Refrigeration minimizes temperature, but can also be expensive to maintain in tropical conditions. We used five tropical seed varieties to compare the effects of these storage methods over the course of one year; our goal was to use the outcomes of this study to help prescribe storage conditions for this seed bank and others like it around the world.