Greenhouse float-bay microclimate.
The temperature of the greenhouse float
water, soilless medium within polystyrene
seeding trays, and ambient air 3 cm above
the soil surface was recorded in two tobacco float greenhouses, one each in Florence and Horry Counties, South Carolina.
Polystyrene seeding trays containing soilless medium (Carolina’s Choice Tobacco
Mix, Carolina Soil Company, Kinston,
NC) were seeded with pelletized tobacco
seed of tobacco cv. K 149. At site 1, float
bays were filled with nutrient solution and
trays were placed immediately upon the
unheated nutrient solution after seeding. At
the completion of seeding, the greenhouse
was heated according to Clemson
Extension recommendations (14). At site 2,
nutrient solution was placed within the
float bay, the greenhouse ventilation
curtains were closed, and the greenhouse
was heated 72 h prior to seeding and
placement of trays on the nutrient solution.
The water within the float bay was heated
by convection and solar radiation. Sites 1
and 2 were seeded on 22 January and 2
February 1997, respectively.
Temperatures in each greenhouse were
monitored after completion of seeding with
Campbell 21X Microloggers (Campbell
Scientific, Logan, UT) with copper-constantan fixed thermocouples. Three thermocouples were wired in parallel to a
common lead and dispersed >1 m apart
within the float bay. Temperatures were
averages for nine readings (three replications × three thermocouples/replication).
Temperature values at seeding for each
micrologger were confirmed with an
Omega digital thermometer (Model HH-
25TC, Omega Engineering, Stanford, CT).
Temperatures were recorded every 10 min
and averaged for each 60-min period. Fertility and insect control were based on
Clemson University Extension recommendations