What is Root Zone Heating
Figure 1 – Root Zone Heating with BioTherm’s MicroClimate Tubing.
With shrinking prices and stiffer competition in the markets, lowering production costs and producing premium crops is more important than ever. One tried and true way is root zone heating in your greenhouse facility. Horticulture engineers have spent years developing heating systems to maintain uniform temperatures within a greenhouse, and all would agree heating from the ground up simply makes the most sense. Root zone heating provides faster root growth, improved yields, and substantial energy savings, i.e. adding money to your bottom line.
So what is root zone heating? Root zone heating systems generally consist of a boiler or hot water heat source, pumps, a heat distribution system, like rubber tubing or aluminum pipe, and thermostat controls (Illustration 101). The benefits of root zone heating to extend a plant’s growing season or increase yields has been recognized by growers for centuries, but not until the 1970’s did growers really begin to utilize this method.
Illustration 102 - Generalized setup for several root zone heating systems.
Before root zone heating, forced air systems were the typical way to heat a greenhouse. But they are expensive to run and far from energy efficient. The air patterns created by hot air systems form pockets of cooler air, making the temperature lower than ideal in certain areas in the greenhouse. Root zone heating counteracts these deficiencies by placing heat directly under the plant and heating from the ground up. BioTherm has been on the cutting of these systems, creating the first commercialized root zone heating systems for commercial horticulture. Root zone heating can be utilized for most any growing method but is most commonly used on benches, floors, and beds (Illustration 201,202).
Illustration 201 – Root zone heating system for the floor using rubber tubing.
Illustration 202 - Root zone heating system for benches using aluminum finned pipe.
Root zone heating provides faster root growth. Optimum root temperature reduces the time to root cuttings and germinate seed. Research has shown root initiation on semi-tropical plants is best at higher temperatures. Flowering bulbs can be forced into bloom at an accelerated rate using bottom heat and germination for specific seedlings is increased by upwards of 30% when soil temperatures were increased from 50°F to 70°F. In some plant species, root initiation was best at soil temperatures of 86°F, which is most easily achieved using root zone heating as opposed to just air heating. And any professional grower knows well initiated and healthy roots leads to a higher producing and healthier plant.
Root zone heating improves yields. By placing heat directly under the plant growers can maintains a more uniform heat pattern than can be obtained with perimeter or forced air unit heaters. Meaning all plants have the same opportunity to produce at their optimum potential. Further, if the root zone temperature is properly maintained, among other variables, the plant has more energy to focus on efficient growth, nutrient uptake and reproduction. Living soils benefit from root zone heating by promoting the growth of beneficial soil microbes. Higher producing plants is half the battle in increasing the bottom line – cutting costs is also important.
Root zone heating substantially saves fuel and saves money. Several studies in the 1980’s and 1990’s found that by using root zone heating as a heat source, compared to perimeter hot water heating to heat the ambient air, savings up to 50% could be achieved. Soil can be heated by the air, but it is more economical to heat the soil directly. High air temperatures increase heat loss from the greenhouse, further driving the need to burn more fuel for additional heat. Generally, growers target for a root zone temperature of 70°-75° with an ambient air temperature that is 5°-10° cooler, which can only be achieved using root zone heating. Research by Rutgers University found that warmer root temperatures allow for a lower ambient air temperature, particularly for vegetative growth. Root zone heating can be a major source for energy conservation and ultimately cutting costs.
Root zone heating is a solution that provides any grower with a more successful crop year after year. Whether growing on a bench, the floor, or in beds, root zone heating can be applied. The benefits of root zone heating over air heat systems has been tested and proven over time. By providing faster root growth, increased yields, and substantial energy savings, it is an option any commercial operation can’t afford to not consider.