It is due also to the presence on the ground of decaying leaves and twigs, or humus.

The water which thus passes into the humus and the soil beneath does not remain there, but slowly seeps downward, and finally after weeks and months emerges at a lower level as a stream.

The composition of the soil and the low temperatures contribute to the low amount of humus and poor decomposing of the organic matter making this soil largely unsuitable for agriculture.

This terrestrial orchid grows in the humus of the understory of trees such as "Coccoloba pirifolia", "Randia aculeata" and "Comocladia glabra".

Certainly, the moist soil, rich in humus, and the climate in the Spreewald also contribute to the good growth in the cucumber fields.

After several years of systematic investigation he concluded that they were made up mainly of humus, which derived from decayed leaves, and sand.

Unlike many soils in which there are easily distinguished layers or soil horizons, a chalk rendzina soil consists of only a shallow dark humus rich surface layer which grades through a lighter brown hillwash containing small pellets of chalk, to the white of the chalk itself.

It can be divided into three general pools: living biomass of microorganisms, fresh and partially decomposed residues, and humus: the well-decomposed organic matter and highly stable organic material. Surface litter is generally not included as part of soil organic matter.

In stable soils, humus dominates the soil organic matter fraction.

Thus most of the benefits and properties of soil organic matter relate specifically to humus.

The amount and type of amendment may depend on many factors, including the amount of existing soil humus, the soil structure (clay, silt, sand, loam etc.), the soil acidity/alkalinity, and the choice of plants to be grown.