The process of separately digging up the topsoil and subsoil layers of a cultivated space and mixing in soil amendments in order to improve soil fertility and aeration.
Double Digging in the Forest Garden
Farmers in the Forest Garden Program learn early on that a good soil structure will provide a healthy base for their Forest Gardens. Double digging is one of the methods that improves soil fertility and structure. It is time and labor intensive, so farmers target areas of the Forest Garden where there will be high-value crops, including a few permagarden beds and tree nursery bare root beds. Because it only needs to be done once and maintained year after year, farmers can double dig additional beds each year until they have applied the technique throughout their entire Forest Garden.
Soil Amendments for Double Digging:
Composted animal manure. It’s important not to apply fresh manure, as the levels of nitrogen and ammonia can burn plants.
Wood ash is a soil pH stabilizer that is rich in potassium and phosphorus. Wood ash should be sourced from a pure wood fire, free of plastic, to avoid harmful toxins.
Eggshells are high in calcium and very beneficial to crops in the cabbage family. Eggshells can be pounded into a fine powder before being added directly to the soil or in a compost pile