Double dug beds

With the double dug bed technique, it is possible to create small productive vegetable gardens. This is done by double-digging the soil and incorporating adequate amounts of manure. This alternative digging process allows the farmer to work the soil deeper and to spread compost evenly along the whole excavation profile. The hard pan that is often formed on tropical soils is broken by the process. This allows aeration and improved nutrient adsorption in the soil. The deep incorporation of compost favours the breakdown of humic components, and reduced loss of nutrients via runoff and decomposing gaseous emissions. The deep cultivation creates a soft medium that allows roots to grow longer and stronger, retains more water and it is likely to increase yields.

Double dug gardens are created in an elongated shape with a width of around 1.5 m. The length can vary, but 7 m is often suggested as ideal (Nandwa et al., 2000). The double dug bed should be narrow enough to be conveniently farmed in every section by standing on its edges. Its establishment entails the cultivation of the designated garden in a stepwise manner by applying one layer of compost or manure and then digging small, adjacent trenches until the whole area is double dug. In the end, the double dug bed will look elevated due to the increased volume of the air voids and the incorporated organic matter. The same procedure must be followed in the following years. After some time the soil will be softer, darker and easier to work (Stein, 2000).

References:

Knoop, L., Sambalino, F., & van Steenbergen, F. (2012). Securing Water and Land in the Tana Basin: a resource book for water managers and practitioners. The Netherlands: 3R Water Secretariat.

Nandwa, S., Onduru, D., & Gachimbi, L. (2000). Soil fertility regeneration in Kenya. Hilhorst, T. and FM Muchena (eds.). 2000. Nutrients on the move: Soil fertility dynamics in African farming systems, chapter 7. London: International Institute for Environment and Development.

Stein, M.R. (2000). When technology fails. a manual for self-reliance & planetary survival (p. 405). Clear Light Pub