Evaluation of zeolite seed 'drying beads R' for dying rice seeds of low moisture content prior to long-term storage
2013
Timple, S.E. | Hay, F.R. | Thavong, P. | Taridno, P.
Four experiments were carried out using zeolite seed Drying Beads to dry freshly harvested rice seeds to low (genebank) moisture content. The beads were mixed with 120 g of seeds in different ratios (between 0 and 3 beads-to-seed, by weight), sealed inside moisture-proof bags or heat-sealed laminated aluminum foil packets and placed in temperature controlled environments for drying and/or storage. The first experiment confirmed that the beads dry seeds very rapidly. The final moisture content of the seeds depended on the ration of beads to seeds and to some extent, on the temperature, with slightly more drying at 30 degrees C compared with 15 or 5 degrees C. When seeds were stored with the beads at either 5 and -20 degrees C, seeds continued to dry. In the first two experiments, insufficient beads (bead-to-seed ratios of 0.97 and 1.06) were used to reach the target moisture content of 6.1%. The lowest moisture content reached was 4.2%, when the quantity of beads was three-times that of seeds. Germination was similar for seeds stored for 371 days at 5 degrees C either with or without the beads after the same initial drying treatment. Those was lower germination of seeds dried at low temperature and then stored at -20 degrees C; however, this was attributed to dormancy. Whilst the water uptake isotherms confirmed the high capacity of the beads compared with silica gel, particularly at low relative humidity, the beads do not work to full capacity in a bead-seed system and the absorption properties appeared to change. Further work is required to optimize the use of these beads for drying seeds to target moisture contents, without either under-dying which could lead to undesirable high rates of viability loss, or unnecessary and perhaps detrimental over-drying.
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