Soil affects productivity and bean quality. Its level of organic matter, minerals, trace elements, micro-organisms and acidity are powerful contributors to a coffee tree’s vigor and to the flavor profile potential of its beans. A soil’s texture, however, is the most important factor for growing sustainable quality coffee, for while a soil’s contents can be “corrected” with inputs such as fertilizers and lime, its texture is far less malleable. Ideal soils should be loamy – crumbly, permeable, having high oxygen content, and be deep, especially in drier areas.
A coffee plant can withstand long dry seasons lasting up to six months if the soil has retained some moisture. In very dry areas, such as Kirinyaga, Kenya, the soils must be especially deep to retain moisture during prolonged droughts; a coffee tree’s roots can burrow at least ten feet (three meters) down. Too much continuous moisture around the root system will, on the other hand, harm the plant. Certain famous farms of the Antigua valley in Guatemala require carved channels to allow for drainage in what was once a marsh.
A further discussion of soils will be made in our section on coffee tree nutrition.