Bull. Spec. CORESTA Congress, Brighton, 1998, p. 84, APOST11

Alternative covers for plant production in outdoor float beds

Central Tobacco Research Institute (CTRI), Rajahmundry (A.P.) India
Techniques for the successful production of tobacco transplants by direct seeding in outdoor float beds have been developed at the University of Tennessee. Germination rates of 90-94 % and plant usability rates of 78-90% have been obtained over a four year period. However, intensive management is required to maintain proper temperatures and to prevent damage from rainfall. A two year study has investigated various shade cloth materials for their ability to prevent excessive heat build-up inside the beds and to prevent rainfall damage to emerging seedlings. Temperatures inside the bed were monitored throughout the plant production period via thermocouples. Data were collected for percent germination and percent plant usability. In 1997, a 60% black shade mesh cover significantly reduced heat build-up inside the beds in comparison to a standard Typar cover. Percent germination (91-93%) and plant usabilities (82-85%) were not significantly different for the two covers. However, plant development was delayed by approximately 7-12 days by using black shade mesh. In field plantings, no premature flowering or ground sucker development was observed regardless of bed cover. Although rainfall damage was not observed in the 60% black shade mesh cover in 1997, 1998 evaluations of 60% black, 57% white, and 38% white shade mesh covers resulted in extensive rainfall damage for all covers. A 55 % shade solid white plastic cover is presently being evaluated. This cover eliminates water damage in the beds and preliminary data indicate that sufficient light is provided to allow normal plant development.