What happens to humus once added to soil?

Thursday, 18 April 2013  |  HOTBIN Composting

First let us check - we are using humus to mean the humic fraction of soil (ie fulvic acid , humic acid and humin), we do not mean 'compost'.

All soil organic matter is eventually decomposed (mineralised) back to carbon dioxide and water. The big difference is most plant waste will return to carbon dioxide quickly (1-5 years), but humus (once formed) survives hundreds of years – it has been routinely carbon 14 dated at 200-500 years old. Humus is often referred to as 'refractory' or 'recalcitrant'.

The amount of  humus in your soil has enormous implications for soil fertility and hence food production. It also acts as a defence against global warming as it is a carbon sequestration material.