One of several new projects you’ll see when you come whitewater rafting at Malode this year is our solar heated planting bed. By heating the root zones of the plants we hope to significantly enhance our production and, with the help of our greenhouse, lengthen our growing season.
The mechanics of it are pretty simple: the sun heats water passively in our black reservoir storage tank. The hot water is circulated by a small solar powered pumped through the grid of pvc pipe that is buried below the growing bed and sandwiched between 6 inches of loose granite and pea gravel. The rock bed radiates the heat into the soil above, heating the roots of the plants.
Using the rock is important because it distributes the heat evenly from the pvc; without it the soil is such a heat sink that we’d have cold spots. Also, it’s important to use rocks that conduct heat well. Dense rock like the quartz in the pea gravel, along with the granite stones we used from digging out the area for the storage tank, are both good conductors.
By using a battery to store power generated during the day, we’ll also be able to heat the bed at night when the soil potentially cools down to temperatures that inhibit plant growth.
Greatly of interest to us is the quantifiable increase of production that this project will attain. The non-heated beds in the garden will serve as a control for our experiment. One thing is for sure though: our planting place is nearly doubled with the addition of this 200 square foot bed, which means we’ll have lots more vegetable to savor in our meals this season on our rafting trips, ropes courses and outdoor education programs.