Tobacco Greenhouse Seedling Production

— Written By Curtis Fountain and last updated by
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NCDA&CS Solution Analysis Report

At this point, you should have your water sample report. In some instances, recommendations note certain nutrients. The following may offer additional interpretation assistance.

Total Alkalinity

The desirable total alkalinity concentration is less than 100 ppm. At concentrations less than 100 ppm, source water alkalinity adjustment is not necessary and should not be made. If the total alkalinity concentration is 100 ppm or more, add battery acid based on the Acid Requirement. Acid Requirement indicates the ounces of battery acid (9.19N sulfuric acid) to apply to each 100 gallons of water for alkalinity adjustment.

Boron

The desirable boron concentration is 1-2 ppm. If boron concentration is less than 1 ppm, use a tobacco greenhouse complete fertilizer that guarantees a trace of boron.

Calcium

The desirable calcium concentration is 20-100 ppm. If calcium concentration is less than 20 ppm, a calcium-containing tobacco greenhouse complete fertilizer or gypsum (landplaster) can be used to suppy additional calcium. Do not add both.  If gypsum is used, apply 3 ounces per 100 gallons of water in the waterbed.

Seedling Germination & Growth

As a general rule, seeding should occur 50-55 days prior to the desired transplanting date. If April 10 is the desired transplanting date, February 19 (50 days) would represent the approximate seeding date.

The ideal germination temperature (tray level temperature) for tobacco seeds is 68 degrees F at night and 86 degrees F during the day. Burning fuel to maintain nighttime temperature above 68 degrees F and reducing ventilation to maintain daytime temperature above 86 degrees F is not necessary for fast, uniform germination. Germination usually requires 7-10 days.After maximum seedling emergence, nighttime tray level temperature can be reduced to 55-60 degrees F. A daytime tray level temperature of 80-85 degrees F is adequate for normal growth. Fuel use decreases 15% for every 5-degree reduction in temperature.  Plant injury due to heat can occur if tray level temperature exceeds 100 degrees F.

Fertilization

Common tobacco greenhouse complete fertilizers (2-1-2, 3-1-3, or 4-1-4 ratios) should perform similarly. The point of emphasis is to apply appropriate concentrations at appropriate times.


For growers utilizing fertilizer injection systems,
a constant application of 125 ppm nitrogen from a tobacco greenhouse complete fertilizer is recommended.For growers without injection systems, the tobacco greenhouse complete fertilizer should be added to the waterbed in 2 steps. Step 1 is:  100-150 ppm nitrogen should be applied to the waterbed within 7 days after seeding. Step 2 is:  4 weeks after the initial fertilizer application, an additional 100 ppm nitrogen should be applied to the waterbed. The additional 100 ppm nitrogen application is based on the total waterbed volume (as is the case for the initial application).The amount of water per waterbed can be calculated by using the following:  length (ft) x width (ft) x depth (ft) x 7.48 gallons/cubic foot.

Salt Injury

High temperatures, low humidity, and excessive air movement promote water evaporation from the growing medium surface. This results in fertilizer salts accumulation in the medium at the top of the cell. High salt levels can injure (burn) young seedlings. This situation should be monitored from seedling emergence until plant roots grow into the waterbed. Consider overhead watering 14 days after seeding to reduce potential salt injury.

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