The timing of Prosopis seed collection and subsequent planting programs can make it advantageous to have some means of storing viable, high quality seed. Before storing, of course, the seed must be properly dried. In storing, the respiration of seed must be reduced to the lowest possible level by lowering storage temperature.
The duration of storage may be short-term, i.e., up to one year, or long-term, depending on the situation. In either case, seeds can be either stored at room temperature or under refrigeration.
If refrigeration is not available, Prosopis seed may have to be stored at ordinary room temperatures, even with daily and seasonal fluctuations. As mentioned above, seed can be packaged in boxes or bags; however, it is more desirable to pack the seed in air-tight containers if storage is to take place at room temperature, to maintain a constant humidity and, if need be, to protect it from insects and other pests. To reduce the humidity and, therefore, prolong viability, desiccating chemicals (such as calcium chloride) in small cloth bags can be placed in the containers with the seed.
Care should be exercised to keep the containers off floors and away from walls, a practice that will help to keep insects, other pests, and dampness away from the containers. Also, the containers should be stored so that air can circulate around them, keeping the seed drier and cooler. Extreme heat can destroy a seed’s ability to germinate.
A more effective method for storing Prosopis seed, even in the short-term, is in air-tight containers at a constant, cold temperature, just above or below 0°C. The moisture content of seed held in cold storage should not exceed a range of 4 to 12 percent. To maintain a check of the moisture content, periodic measure should be taken, as follows: remove a small sample of seed from cold storage and weigh; dry the seed in an oven at 105°C for 16 hours and reweigh; and, calculate the moisture content of the seed in percent by:
Percent moisture content =
A cold storage facility is normally an insulated and ventilated room, cooled by refrigeration units. However, such an installation may not be available due to financial or other reasons, in which case a useful alternative must be sought. For example, large household refrigerators can often be used for the storage of at least small quantities of seed.
In the absence of an energy source, a storage facility can be built by using cork or wood planks with layers of straw between them. Temperatures in stores of this kind will fluctuate less than that on the outside; in general, this is good, as seed will maintain its viability longer in conditions where temperatures do not undergo wide fluctuations. A store of this construction, which is relatively inexpensive to build, should be so planned that refrigeration units can be added later, if an energy source becomes available.
Regardless of the approach, extreme care must be exercised to prevent any fluctuations in temperature and moisture, both of which are most detrimental to the storage of the seed.
Most of the above discussion relative to the short-term storage of seed also applies to long-term storage. But, the longer the period of storage, the more important it becomes to maintain a continual monitoring of the environment within a storage facility.
Air dried Prosopis seed that is stored at room temperatures can remain viable for several years. In one instance, Prosopis juliflora seed that was air dried and stored at room temperatures in a herbarium in the southwestern United States maintained satisfactory viability (60%) for 50 years. However, once again, the most effective way to store seed, particularly for a period of 3 to 10 years, is within a cold storage facility.
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