|As fallen leaves and the remains
of other organisms decay they produce humus. Humus is a collection of black
or brownish organic (carbon containing) matter that continues to decay
slowly. To see humus, inspect a compost bin.
Humus acts as an important reservoir of nutrients for plants, and assists in the retention of water by soil .
One way of measuring humus content is to take soil back to the laboratory, dry it completely, and then heat it so that all the organic matter burns. By measuring the mass before and after, you can figure out how much organic matter there was.
However, since the sand on Stradbroke is quite white, and humus is dark, you can use the colour of the soil/sand to estimate humus content. Can you think of any other ways?