Another season extender, Agritape, a heating element that goes under seedlings, is manufactured by coating a sheet of polyester with a resistive-conductive ink. Flat copper conductors are added to the sides of the coated surface to power the heater and another sheet of polyester is added to seal up the Agritape. Agritape is manufactured in long rolls 11 inches wide and and can be cut to construct individual heaters of any length up to 25 feet. An 8-foot electrical cord is attached and the cut ends are sealed with liquid plastic. The coating heats up when it is electrified with standard house current (110 volts AC) and will generate heat (95 degrees F) that is extremely uniform across the entire surface of the tape. The tape is rated 20 watts per linear foot.
An Agritape system consists of a control unit to regulate soil temperature, the Agritape heater(s), and a grounded screen. The screen serves to protect the tape from physical damage, to safely ground the current if the tape is penetrated, and to draw off static electrons that collect on the surface of the tape(The tape acts as a capacitor when it is in operation). The flow of static electricity can trip GFCI outlets if the system is not well grounded. The screen also holds the tape in position on the bench.
Thermostat Sold Separately
To install a system, roll out the heater(s) and plug it into the control unit. Cover the heater with the ground screen. Connect the ground wire from the control unit to the screen. Plug in the control unit and place the bulb thermostat in the soil of the seed tray or container. Set the dial to the desired soil temperature. Insulation board may be installed under the heater to improve thermal efficiency, but is is not necessary. Ambient temperature should be kept at 50 degrees F or higher as the Agritape will increase soil temperature by a maximum of 20 degrees. The best application of an Agritape system is in small seed starting and propagation operations. The system is easily installed and removed so bench space is available for other uses. The system features precise temperature control resulting in high germination rates and uniform crop development. Soil temperatures are regulated by plus or minus 1 degree.