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<br />that meal from blood, feathers, meat, crab shells, fish, cot-
<br />tonseed and whey by- products increased shoot weight by
<br />57 -83% over rion- fertilized plants. The results of this study
<br />are shown below.
<br />Fertilizer
<br />N -P -K
<br />Shoot wt. (grams)
<br />Crab -shell meal
<br />8.2 -1.5 -0.51
<br />8.8
<br />Blood meal
<br />12.5- 1.1 -1.0
<br />18.5
<br />Dried whey sludge
<br />5.3- 2.5 -0.9
<br />18.3
<br />Feather meal
<br />13.6- 0.3 -0.2
<br />17.3
<br />Fish meal
<br />10.1- 4.5 -0.5
<br />17.1
<br />Meat meal
<br />7.7- 3.1 -0.7
<br />16.3
<br />Cottonseed meal
<br />6.5- 1.1 -1.6
<br />16.2
<br />Fish -scale meal
<br />10.0- 3.7 -0.1
<br />15.8
<br />Distiller's dried grains
<br />4.3- 0.9 -1.1
<br />14.5
<br />Soybean meal
<br />7.5- 0.7 -2.4
<br />14.4
<br />Wheat bran
<br />2.9- 1.4 -1.3
<br />13.5
<br />Alfalfa meal
<br />2.5- 0.3 -1.9
<br />10.8
<br />Canola meal
<br />6.0- 1.1 -1.3
<br />10.8
<br />None (control)
<br />0 -0 -0
<br />10.3
<br />Irrigation
<br />Thorough, even watering is extremely important to plug and
<br />transplant production success. Water stress sets plants back
<br />and increases the chance that they will fare poorly once
<br />planted outdoors. Automatic or semi- automatic watering
<br />saves a great deal of work, but will not eliminate the need
<br />for "touch -up" watering by hand, on a regular basis. The
<br />plants will do best, especially when in plastic trays, if they
<br />are supported off the ground to allow good air circulation
<br />and prevent waterlogging. As a general rule they should not
<br />be watered in late afternoon, lest they remain overly wet
<br />through the night.
<br />Plug cell size will also affect the watering schedule. While
<br />in larger containers water must be added to thoroughly
<br />moisten the entire medium profile, in shallow containers a
<br />less than saturating amount of water can be added without
<br />detrimental effects to roots since the water will distribute
<br />adequately.
<br />One of the most common problems in greenhouses is over -
<br />watering. Not only does this contribute to poor plant growth
<br />and health, it also encourages the spread of pathogens that
<br />thrive in wet conditions. Overwatering is especially easy to
<br />do with young plugs; underwatering becomes a problem
<br />with older plugs.
<br />There are five major ways 'to water plugs: 1) hand watering,
<br />2) stationary sprinklers, 3) traveling boom sprinklers, 4)
<br />fog, and 5) subirrigation. Of these, hand watering and subir-
<br />rigation are most appropriate for small growers. The biggest
<br />problem with hand watering is, of course, labor expense. It
<br />is also less uniform than mechanized systems. Subirrigation
<br />eliminates both of these problems but can result in over -
<br />watering because of immediate saturation. Subirrigation is
<br />better when growing larger plugs.
<br />New Research on Irrigation
<br />A recent study at the University of Georgia showed that
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<br />moisture stress tends to increase aphid populations on New
<br />Guinea impatiens and marigolds, but has little effect on spider
<br />mite or thrips populations. In experiment, mite populations
<br />were lower on ageratum plants that were irrigated with an ebb -
<br />and -flow system, compared to overhead - irrigated plants.
<br />Researchers at North Carolina State University found that envi-
<br />ronmental conditions, rather than plant growth, may dictate
<br />irrigation practices. Their other findings were:
<br />• Plugs do leach fertilizer, sometimes heavily.
<br />• Plug trays (288s) can take 500 -1000 ml of water per tray
<br />at each irrigation, depending on environmental conditions.
<br />• Winstrip trays used more water and dried out faster than
<br />conventional trays.
<br />• Plants tended to be larger in Winstrip trays and finish ear-
<br />lier than in conventional trays.
<br />• Plants may use less than 2% of the water applied to the
<br />tray.
<br />• Water per tray may be affected more by air humidity than
<br />by temperature or plant condition.
<br />Light
<br />Although supplemental lighting can increase transplant quality,
<br />it is generally not needed for most operations. The exception to
<br />this rule of thumb is in winter, especially in northern areas of
<br />the U.S. Low light levels result in "leggy" plants, so growth
<br />regulation techniques are even more important in these kinds of
<br />situations. Most growers use high intensity discharge (HID)
<br />lamps to light their greenhouses.
<br />Growth Regulation
<br />Plugs and transplants can often elongate due to light competi-
<br />tion, and growers end up with spindly, leggy plants. Conven-
<br />tional growers use chemical growth regulators to combat this
<br />problem. There are, however, other, non - chemical means to
<br />control growth. Brushing is a kind of mechanical conditioning
<br />whereby the grower uses a tool (like a broomstick, piece of pa-
<br />per, or PVC pipe) to brush the plant tops and reduce their
<br />height. According to Garner et al., "Research concerning the
<br />effects of mechanical stimulation on floricultural crops is con-
<br />siderably more limited than that on vegetable crops, probably
<br />due to the availability of chemical growth regulators approved
<br />for use on bedding plants ".
<br />Researchers at Cornell studied the best ways to brush plants.
<br />They used a piece of polystyrene foam on tomato seedlings and
<br />found that ten strokes a day was enough to reduce the height by
<br />about 20 %. Using more than about ten strokes a day was inef-
<br />fective, and there was no difference between applying all the
<br />strokes at one time or spreading them out over a longer period.
<br />No matter what the seedling height was when brushing began
<br />(6, 8, or 10 cm), the reduction in height was 3 mm per day.
<br />In another study, researchers studied the effects of brushing on
<br />tomatoes and on four species of bedding plants (geranium, im-
<br />patiens, petunia, and pansy). For the tomatoes, they found that
<br />10 -20 daily strokes were enough for height control, that there
<br />was no difference between morning and afternoon brushing,
<br />
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