Australian soils are notoriously lacking in carbon. Increasing the amount of organic matter (carbon) within our soils can improve them dramatically. This can assist in water retention and drainage as well as general soil and plant health. It can help gardeners to think about carbon as coming in three colours – Green, Brown and Black.
Green Carbon includes cover crops, chop-and-dropped weeds, and liquefied green plants such as sprouted seed tea.
Brown Carbon includes things like composted plant material and aged animal manures.
Black Carbon is charcoal in the form of bio-char which can be also be transformed into terra-preta (black earth).
By using all three types of carbon we can greatly improve our garden soil. There are many ways in which to do this and just a few examples and recipes can be found here.
The picture on this page illustrates how poor sandy soil (top) can be greatly improved (middle) by the addition of different types of carbon (bottom).