This article is from ECHO Asia Note # 38.
Introduction
Given the proper facilities necessary to store seeds long-term, whereby low temperature and low humidity are kept stable over time, it is very possible to store most orthodox seeds for several years at a time in the tropics (Harrington, 1972). Unfortunately, implementation and maintenance of the proper facilities can be very costly and many existing seed bank and gene bank facility examples do not satisfy the needs of many smaller organizations or communities. Thankfully, many diverse options currently exist, with varying levels of investment for a wide range of facilities, from expensive, high-tech facilities down to low-cost, low-maintenance models. At ECHO, we operate our own range of seed storage facilities at our various seed banks around the world, from a high tech, walk-in climate-controlled cold storage room, to a retrofitted refrigerated shipping container, to a low-cost, foam-insulated cold room cooled with a standard split-unit air conditioning system.
While each of these systems has proven to be effective in storing seeds for our needs over time (Motis, 2016), even our lower cost options do not adequately address the very real question of how seed storage facilities may be replicated at a farm or local community level. Though we have learned how to bring down costs considerably to establish low-budget facilities, these options remain out of reach for many communities and smaller organizations, and each example currently relies on the need for an uninterrupted supply of electricity, among other barriers. In an attempt to address these ongoing questions, much of our recent effort at the ECHO Asia Seed Bank has shifted into improving the practicality and cost-effectiveness of seed storage options for small Community Level Seed Banks, and on down to the individual farm level.
Building on ideas observed in the field, and storage ideas passed onto us by ECHO network members (CRS, 2014), we attempted to verify the effectiveness and practicality of various options using natural earth-building techniques. A small research experiment was implemented over the course of 2018 (Jan – Dec) at the ECHO Asia Seed Bank in Chiang Mai, Thailand, and was replicated by one of ECHO’s Community Level Seed Bank Network members in Myanmar.
Comparing Earth Bag Houses, Hillside Bunkers, and Buried Cisterns
It has been suggested for many years now that various natural building facilities such as earth bag and rammed earth houses may serve as ideal sites for storing seeds, while in other places it has been suggested that storing seeds underground may be effective as well. Keeping in mind the insulating qualities and low-cost of construction of natural building techniques (Build Abroad), we began testing different methods at the Asia Impact Center. In 2018, ECHO conducted a small experiment in Thailand and Myanmar to test these hypotheses, specifically within the Southeast Asian context, where temperature and humidity are higher than the climates in which these facilities have previously been implemented.
Using lablab - Lablab purpureus (L.) - seeds were stored over the course of one year inside of three different natural building facilities, including (1) an Earth Bag House, (2) a Hillside Bunker, and (3) a Buried Clay Cistern (Figure 1). Seeds were placed inside of each facility, with half of the seeds being (A) Sealed in jars using a modified Bicycle Vacuum Pump (Bicksler, 2015; Thompson, 2016), while the other half remained (B) Unsealed in Paper Bags. Four separate batches were placed in each storage facility in order to test seeds for Seed Moisture Content and Germination rates over the course of months 3, 6, 9, and 12, with containers remaining unopened until testing during their respective months.
In addition to testing and monitoring the viability of these seeds stored in these environments, data loggers were placed inside and outside of each of these facilities to track storage conditions over the course of one year, specifically temperature and relative humidity. Data loggers recorded temperature (oC) and relative humidity (%) every hour.
A Story of Stabilized Storage Conditions
Climatic data collected from the Thailand site generally indicate a significant stabilization of temperate and humidity in the Earth Bag House and Buried Cistern compared to Outside Ambient conditions (Figure 2). Temperatures did not drop considerably on average in each
of the storage facilities (~23oC), but daily temperature swings were reduced substantially. For reference, our climate-controlled, walk-in seed storage cold room in Florida maintains an average temperature of 6oC, with very little fluctuation, while our spray-foam insulated cold room using a standard split-unit air conditioning system maintains an average temperature of 15oC.
Relative humidity inside of these natural building facilities was very high overall, even during the dry season (Figure 3). The underground facilities, the buried cistern and the hillside bunker, recorded very high rates of humidity, while the freestanding earth bag house appears to have achieved lower overall humidity. Conditions in the hillside bunker were so humid that our data logger shorted out within days, prohibiting us from recording conditions within.
Good News, if Sealed Properly
On their own, these natural earth-building facilities appear to be poor storage facilities for seeds, due to their high rates of relative humidity, which can quickly deteriorate seed quality. In both Thailand and Myanmar, seed germination rates of unsealed seeds plummeted from 94% to less than 50% within just 3 months of storage (Figure 3). Measuring seed moisture content showed a rapid absorption of moisture in seeds, due to the high moisture content of the air within, rising from 12% seed moisture content to over 20% in just 4 months. Similar results were found when storing seed in vacuum-sealed and unsealed conditions in a refrigerator, where humidity is similarly high (Croft, 2012).
However, in combination with vacuum-sealing, seed germination rates in each of the 3 storage facilities remained steady over the course of one year, maintaining germination rates above 90% at the end of the experiment. Seed moisture content held constant for the most part as well, increasing less than 2% over the course of the year.
This combination of best practices, of sealing seeds with a vacuum and placing them within a stable storage environment, appears to offer an excellent and affordable option for storing seeds in the tropics. Without any use of electricity or external cooling systems, these techniques were successful in terms of storage and adequately maintained seed quality and viability for a full year. Certainly, work in this area needs to continue to seek answers to questions of how much longer seeds can be stored in this manner, and attempted with different seed types as well, but this is good news overall.
Economic Summary of ECHO Seed Storage Facilities
Over the years, ECHO has scaled its various seed banks around the world to the specific needs of the individual seed bank. Each has its appropriate scale and serves different purposes, from distributing thousands of seed packets a year, to serving the needs of a single community or region. Therefore, we deemed it pertinent to share with our network the costs of implementing these different options, to be used as reference points for various levels of seed storage facility options (Figure 4). Note that these prices may vary considerably depending on your location and access to materials and/or labor, and existing structures that being retrofitted.
It is important to note that the higher-cost options listed above are designed more for multi-year storage of seeds (such as in a seed bank or gene bank setting), while the lower-cost options are designed more for community or farm-level settings where seeds only need to be stored year to year, or 2 years at most.
Conclusions
While this data may speak more to the necessity of vacuum-sealing than to the efficacy of natural earth-building techniques for seed storage, it is important to note that in a recent ECHO seed storage experiment we found that vacuum-sealing on its own was not enough to maintain adequate seed viability over the course of one year in Thailand’s tropical conditions (unpublished work). Vacuum-sealed seeds stored on a hot outdoor porch did perform well compared to unsealed seeds, but germination rates still declined considerably. The ability to maintain high germination rates over the course of the entire year in this experiment leads us to believe that the combination of vacuum-sealing AND storage in a stabilized environment are what led to extremely effective seed storage practices in this experiment. ECHO will continue to build on this work to find low-cost, practical options for storing seeds in Community Level Seed bank settings, using practices that are simple and replicable.
Acknowledgements
We would like to extend our appreciation to our partners at the Kahelu Small Farm Resource Center in Myanmar for the collection of data, and the work they have put into establishing their own Community Level Seed Bank. We would also like express our gratitude to the Presbyterian Hunger Program and its faithful donors for their ongoing support of this Seeds of Hope Initiative. Thank you to Luke and Marcie for your help setting up this research.
REFERENCES
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Catholic Relief Services. 2014. Improved Seed Storage Briefs. Nairobi: Catholic Relief Services. Available:https://www.crs.org/sites/default/files/tools-research/seed-storage-briefs.pdf
Croft, M., A.J. Bicksler, J. Manson, R. Burnette. 2012. Vacuum Sealing vs. Refrigeration: Which is the Most Effective Way to Store Seeds. ECHO Asia Notes.14: 1-6. Available: https://www.echocommunity.org/en/resources/5262cfab-ddcf-42ec-843a-82f8468f0829
Harrington, J.F. 1972. Seed Storage and Longevity. Edited by Kozlowski, T.T. in: Seed Biology. 3:145-245.
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Motis, T.N. 2019. Vacuum Sealing Options for Storing Seeds: Tehnologies for Small-Scale Seed Banks. ECHO Technical Notes. 93: 1-16. Available: https://www.echocommunity.org/en/resources/690545ac-4de7-4cc2-9654-70953d2c21bc
Price, Z. 2016. Constructing an Improved Cold Room for Seed Storage. ECHO Asia Notes. 27: 1-5. Available: https://www.echocommunity.org/en/resources/3171bfa2-b742-40d2-9ae1-5dc4da827628
Thompson, K. 2016. Seed Saving in the Tropics: Lessons Learned from the Network. ECHO Asia Notes. 28: 1-5. Available: https://www.echocommunity.org/en/resources/c2b5d0e2-8bd1-48f5-898e-1e5d0b993211