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Home → Publications → National Nursery Proceedings → 2009 → Equilibrium Relative Humidity as a Tool to Monitor Seed Moisture

Equilibrium Relative Humidity as a Tool to Monitor Seed Moisture

Karrfalt, R. P. IN: National Proceed­ing: Forest and Conservation Nursery Associations -2009. USDA Forest Service, Rocky Mountain Research Station, Proceedings RMRS-P-62, p. 43-45. 2010.

The importance of seed moisture in maintaining high seed viability is well known. The seed storage chapters in the Tropical Tree Seed Manual (Hong and Ellis 2003) and the Woody Plant Seed Manual (Bonner 2008a) give a detailed discussion and many references on this point. Working with seeds in an operational setting requires a test of seed moisture status. It is necessary to know if the seeds are high in moisture or if they are dry enough to store without losing germination. Seed moisture testing was originally done by drying seeds for about 16 hours in a hot oven to drive off the water in the seeds. The moisture content was then determined indirectly by weight loss. For example, if there is a 1 g weight decrease after drying 10 g of seeds, the moisture content is assumed to be 10%. The test is destructive because the high temperature required to drive off the moisture will kill seeds. Seed moisture content determined by the oven method can be related to readings taken by an electronic moisture meter. Charts can be made that allow a meter reading to be converted to moisture content. This is a quick, non-destructive test, but requires development of charts for every species. In addition, the seeds must be clean and of high viability. A quick, non-destructive, and simple method of testing the moisture status of seeds is now available that combines the best features of oven tests and moisture meters. This method is equilibrium relative humidity or ERH. Baldet (2007) and Baldet and others (2009) have used this technique with tree seeds. This paper will give some practical description of how the test works and how to use it based on experience at the USDA Forest Service National Seed Laboratory.


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Author(s): Robert P. Karrfalt

Publication: National Nursery Proceedings - 2009

Event: 2013 Winter Forest Nursery Notes
2013