Double digging is a gardening

Gardening

Gardening is the practice of growing and cultivating plants. Ornamental plants are normally grown for their flowers, foliage, or overall appearance; useful plants are grown for consumption , for their dyes, or for medicinal or cosmetic use...

 technique used to increase soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

 drainage and aeration. It involves the loosening of two layers of soil

Soil

Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...

, and the addition of organic matter.

Double digging is typically done when cultivating soil in a new garden, or when deep top-soil is required. On poor or heavy soils, or for vegetable gardens, double digging might be required every 3-5 years. In other cases, double digging is only really needed on starting a new garden, or on total replanting.

First the top layer is dug off with a spade, forming a shallow trench, and then the under-layer (at the bottom of the trench) is dug with a fork. When breaking up the lower layer, organic matter such as compost

Compost

Compost is organic matter that has been decomposed and recycled as a fertilizer and soil amendment. Compost is a key ingredient in organic farming. At its most essential, the process of composting requires simply piling up waste outdoors and waiting for the materials to break down from anywhere...

 is usually added to the soil. If the soil is in need of other minerals like gypsum

Gypsum

Gypsum is a very soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is found in alabaster, a decorative stone used in Ancient Egypt. It is the second softest mineral on the Mohs Hardness Scale...

 or phosphorus

Phosphorus

Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...

this can also be added here.

A second trench is then started, backfilling the first trench. This process is repeated until the whole bed has been treated. There will be soil left over from the first trench, which is used to fill the last trench.

Walking on top of the bed will crush/flatten it, so the gardener must be sure to protect the double-dug garden from too much foot traffic.

External links

• http://www.rhs.org.uk/advice/profiles0105/double_digging.asp
• http://www.farm-garden.com/feature/double_digging_gardeners_workout
• http://www.organicgardening.com/feature/0,7518,s1-5-19-934,00.html