Soil temperature is vital to plant growth and health. All plants react to certain stimuli, such as light, oxygen levels, and soil temperature. When the plant is in conditions that are favorable, it will grow and remain healthly, but if these stimuli change or lessen, it can negate growth and cause sickness. Soil temperature plays a vital role in this process, as the winter months drop the temperature of the soil to low levels, leading to unhealthy plants. Soil heating places a heating source either directly in the soil, or beneath the plants, and keeps the soil itself at a constant temperature, ensuring continued success of the vegetation.
The systems used for soil heating work from the idea of radiant heat. The system uses a heating source (for example, an electrical resistance wire) to radiate heat into the surrounding soil, increasing and maintaining the temperature of the soil. Electrical soil heating systems run off of a standard power outlet, and operate on low power usage. Electrical systems have two variations: in soil heating and under soil heating.
With in soil heating, the resistance wire is ran directly through the soil of the plants, lending the heat directly to the roots. The system is still run off of a standard power outlet. These systems are ideal for outside green houses, where the plants stay within the structure, or for outside gardens that do not contain any potted plants which can be moved in cold weather (such as vegetable gardens). These are especially ideal for commercial application.
Under soil heating takes the form of a heated mat. The mat simply rolls out onto the shelf which the plants sit on. It sort of functions like an electric blanket under the roots of the vegetation. The mat is portable and plugs into standard power outlet. These systems are perfect for the home gardener, who might have a smaller greenhouse, or has potted plants that are transportable.