mrbungalow

I have heard you need to cover a fairly large area with translucent plastic for this method to be effective, maybe 6 X 6 feet at the very least. Remember, there is alot of moisture in soil and it takes alot of energy to heat up a given volume. And heat travels. Taking it a bit far, it could be compared to heating a small area in a swimming-pool; The energy will travel around the volume of water. The energy will also in this case be absorbed into the soil around.
Still, since the ground is more solid, it is possible to heat a portion of the soil. Big, dark rocks under the plastic will help as these act as reservoirs for heat, taking up heat during the day and giving off heat during the night.

I have also heard covering an area with dark plastic is no use at all. The top of the plastic will get very hot, but not much energy will be absorbed into the ground.

Erlend

__________________