![]() Liquid CO 2 is the preferred source because of its purity. Supplemental CO 2 is delivered to ensure a target of 800 to 1000 ppm. The relative humidity is reduced to 70 to 75 % (VPD of 5 to 6 g/cm3). Once the seedlings have emerged the root zone temperature is reduced to 23☌ and the air temperature is maintained at 25☌. Adjacent rows of lights are spaced 3.5 meters (12 feet) apart. ![]() This can be achieved by using 400 W (high pressure sodium) lights placed in rows 2 meters (6 feet) above the seedlings, with 3 meter (9 feet) spacings between the lights within the row. Supplemental light is applied to the emerging seedlings at 160 Watts/m 2 for 16 to 18 hours per day (Fierro et al 1994, Portree 1996). opening up the tunnel slightly to allow air to circulate by the plants for a few days prior to complete tunnel removal. Be sure to condition the plants to the greenhouse environment before removing the tunnel completely by. Once all the seedlings have emerged the plastic tunnel is removed. Seedling emergence is usually complete within 10 days after seeding. The rockwool plugs are often covered by a plastic tunnel to help maintain the optimum humidity. The relative humidity in the nursery should be maintained at 75 to 80% (VPD* of 3 to 5 g/cm3) until the seedlings have emerged. Air temperatures should also be maintained at 25☌. The temperature to the root zone should be maintained at a constant temperature of 25 to 26☌ for the first two weeks while the seeds are germinating and the young seedlings begin to establish. Use light applications of the 0.5 mmho E.C. The seedlings will require watering almost daily at this stage. As long as the feed solution is able to drain away from the bottom of the plugs, water logging should not occur.Ī general rule is to apply feed solution just to the point where it just begins to run-off from the bottom of the plugs. The goal is to maintain moisture levels in the plugs without water logging. of 0.5 mmho and a temperature of 25 to 26☌ is used to wet the plugs as required. The rockwool plugs must not be allowed to dry out or the seedlings can be severely damaged. A typical standard feed solution for tomatoes is presented in Table 1. The feed solution is prepared by diluting a standard tomato feed solution (approximately 2.5 mmho E.C.). Always use quality rockwool rooting media. of 0.5 mmho, a pH of 5.8 and a temperature of 25 to 26☌. Seed is placed directly into rockwool plugs that have been soaked with a seedling feed solution with an electrical conductivity (E.C). The crop is seeded approximately November 15. Fresh seed is also important as seed older than one year can have reduced germination rate and vigour. The propagation area or seedling nursery area must be cleaned and disinfested prior to use.
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