Journal of the Japanese Society for Horticultural Science 67:1121-1123. 1998.

Mechanical conditioning for controlling excessive elongation in transplants

Thomas Björkman

Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

ABSTRACT   Excessive stem elongation in transplants hinders mechanical transplanting and reduces plant survival in the field. Mechanical stimulation is an effective method for reducing stem elongation during transplant production. This investigation determined how to optimize the treatment and the consequences it has on subsequent field performance. This research examined the effects of varying the dose, the interval between brush strokes during stimulation, the time of day that stimulation was applied and the time application was started.  Tomato seedlings grown at 2100 plants per m2 were reduced in height by 20% when brushed with 10 strokes per day from canopy closure until they were ready to set out. More intense treatment did not further reduce the height. The interval between strokes could range from none to 10 minutes with no difference in the effect. The treatments were similarly effective whether applied in the morning or in the late afternoon. Treatments begun at different canopy heights were shorter in direct proportion to the number of days of treatment. The plants grew 6 mm per day when they were not treated and 3 mm per day during treatment.  In the field, treated and untreated processing tomatoes recovered from transplant shock equally  based on the resumption of elongation growth. Leaf area development  and yield were also equal. Furthermore, fresh-market tomatoes were unaffected in earliness, and no treatment-related defects were noted in the fruits. Treated plants were more tolerant of wind. In wind-tunnel tests, treated plants resisted wind speeds about 4 km/h higher. A field planting subject to 70 km.h-1 wind had 12% mortality in untreated plants but only 2% in treated plants. Mechanical conditioning with brushing and impedance produced transplants with desirable qualities without adverse effects on field performance.

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