Definition - What does Double digging mean?
Double digging is exactly what it sounds like – digging through two layers of soil to improve drainage and aeration, while adding organic matter like compost to support better plant health and growth.
MaximumYield explains Double digging
In order to grow and thrive, plants need air, water, nutrients and sunlight. All but one of those is primarily found in the soil. Obviously, soil preparation is crucial to overall plant growth and health, particularly when planting an in-ground garden. While tilling can help ensure that the top layer of soil is broken up, it is often not enough. Double digging your beds will help ensure better aeration, drainage and access to nutrients.
Double digging is nothing more than digging two shovel heads in depth. The first shovel head of dirt is set aside, and then another is dug out. However, the two layers are not mixed. The subsoil layer is broken up, and then organic matter is added. After this, the topsoil layer is placed back where it was. This is particularly important in areas with heavy clay soil, or in areas with sandy soil in which you need to add organic matter to improve soil nutrition or drainage.
As a gardening practice, you’ll find double digging used as a cornerstone in many permaculture efforts, but also in square foot gardening and other high-yield gardening methods. In recent years, there has been some controversy over the benefits and drawbacks of double digging. Some scientific research noted that double digging did not result in improved garden health when compared to no-dig methods, such as lasagna gardening or the creation of hugelkultur swales.
With that being said, double digging remains a time-honored and effective way of improving soil performance in areas with poor soil quality, heavy soil types, or compaction.