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Seed Drying

Seed Drying. Seed Moisture Management And B uilding Pressurized Dryers. Dry air (Relative humidity is below 30%). Water leaves the seed and goes into the dry air. Moist seed. Humid air (relative humidity is above 30%). Water moves from the air into the dry seed. Dry seed.

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Seed Drying

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  1. Seed Drying Seed Moisture Management And Building Pressurized Dryers

  2. Dry air (Relative humidity is below 30%) Water leaves the seed and goes into the dry air. Moist seed

  3. Humid air (relative humidity is above 30%) Water moves from the air into the dry seed. Dry seed To keep seeds dry they must be sealed in a moisture proof container.

  4. Humid air (70%) Water moves both ways or not at all. Moist Seed The condition of a high equilibrium relative humidity. At equilibrium this seed will measure an ERH of 70%.

  5. Dry air (30% relative humidity) Water moves both ways or not at all. Dry Seed The condition of a low equilibrium relative humidity. At equilibrium this seed will measure an ERH of 30%.

  6. Probe Sample holder A water activity (Aw) meter used to measure ERH. Meter Water Activity Meter

  7. Hand held hygrometer

  8. Hygrometer measuring ERH of seeds in a covered box

  9. Peanut butter jar lid with hole bored to fit ½’ pvc pipe Half of ½” pvc pipe coupling Half of ½” pvc pipe coupling ¾” length of ½” pvc pipe PVC pipe and coupling form an acceptably air tight port for the hygrometer probe

  10. Fraxinusamericana seeds Peanut butter jar used as an ERH test chamber

  11. Isotherm of Seed Moisture Free Water Tightly Bound Water 25 Moderately Bound Water

  12. 30 25 Isotherm of Seed Moisture more variation in mc than ERH Good ERH for Seed Storage

  13. Key points of ERH • Can be used on any seed lot regardless of • Viability • Purity • Stage of extraction • Species • No conversion charts needed • Traceable standards available for calibration • Non destructive • Fast – Results obtained in a few minutes • Very easy to use • Low cost equipment ($200 to $2500)

  14. Drying seeds: Key points • Seeds that can be dried to low moisture content are called orthodox. • Controlling moisture is the single most important factor in preserving seed viability. • A pressurized drier is the fastest and most efficient way to quickly and uniformly dry orthodox seeds to preserve maximum viability. • The air in the drier should be 30 to 35% RH. • This is most easily done by putting the drier in a dry room that is at 30% relative humidity (test the humidity with a hygrometer). • Seeds will be dry in 24 to 48 hours. • Test the seed with a hygrometer to know they are dry.

  15. Water escapes from surface seeds only to dry air. Seeds in acontainer or pile can only dry at the surface of the seed mass. Seeds at the lower layers stay moist and are vulnerable to deterioration.

  16. Water escapes to atmosphere Seeds in a pressurized drier can dry quickly and uniformly because air passes around all the seeds carrying away the moisture. Fan Bottom plenum is pressurized with dry air (30%rh) Seeds at the lower layers finish drying first (drying front).

  17. 5 gallon bucket paint strainer holds the seeds. A five gallon bucket serves as the plenum.

  18. Drier viewed from the top.

  19. A collar is needed between each tray to seal in the air and keep the drier pressurized. Multiple trays can be stacked to dry larger lots or several lots simultaneously.

  20. Collars are made by cutting out the center of the bucket lid and lining the edge with weather stripping.

  21. Shaded pole blower motor mounted to bottom of bucket. Blower needs to operate between 1 to 2 inches water column static pressure (wc sp)

  22. Wooden blocks hold the bucket off the work surface to allow air to enter the fan. Screws are place through the mounting brackets on the fan into the blocks which secures both blocks and fan motor. Flexible cable connector Air inlet for the fan motor. (The safety screen removed for illustration.) Six foot extension cord makes a ready made power cord.

  23.  Enlarge Image The blower motor

  24. Barrel size, 22” diameter, strainer for larger seed lots No collar was required for these particular trays.

  25. Vendor and Material List • usplastic.com • ES Strainer • 600, 400, 200, 100 mesh (higher number is larger hole) • 5 gallon pail size: $4.31 each • 55 gallon drum size, 22”: $12 to $13 each • 5 gallon Bucket $4.30 + lid $1.82 • grainger.com • Induced draft blower Dayton 4C723 $122.50 • Extension cord, Romex connector, wire nuts • Local sources • Weather stripping, pan head screws, 2x2 wood blocks, hardware cloth to cover blower inlet

  26. Long term storage • Must first be dried with air at 30% relative humidity or less until dry • Seal in a moisture proof container • 4 to 6 mill poly bag • Plastic bottle or plastic dish with a tight lid • Freeze the seed

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