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Organic matter influences physical properties of soils far out of proportion to the small quantities present. Furthermore it supplies energy and body building material for the micro-organisms, whose activities which were considered in my last post.

Sources of soil organic matter

The original source of the soil organic matter is plant tissue. Under natural conditions, the tops and roots of trees, shrubs, grasses and other plants annually supply large quantities of organic residues. In a garden soil, a good portion of cropped plants is commonly removed with some tops and roots being left in the soil. As these materials are decomposed and digested by soil organisms of many kinds, they become part of the underlying soil horizon.

The fermented food waste added from ZingBokashi composting systems is composed mainly of plant residues so therefore is a great source of food for the various soil organisms plus contributes organic matter (more details at, so essential to soil formation.

Signs of microbial activity in the soil following burial of ZingBokashi fermented food waste.

Signs of microbial activity in the soil following burial of ZingBokashi fermented food waste.

Animals are usually considered secondary sources of organic matter. As they attack the original plant tissues, they contribute waste products and leave their own bodies as their life cycles are consummated. Certain forms of life eg earthworms, centipedes ants and beetles, also play an important role in the translocation of plant residues.

Composition of plant residues.

The moisture content of plant residues varies from 60 to 90 percent, with food waste being around 80 percent. More than 90 recent of the dry matter is carbon, hydrogen and oxygen with other elements playing a vital role in plant nutrition and in meeting micro-organism requirements. Nitrogen, sulfur, phosphorus, potassium, calcium and magnesium are significant, as are micronutrients.


Soil organic matter is all the plant and animal residues at various stages of decomposition, cells and tissues of soil micro-organisms and substances formed from soil fauna and microbes found in or on the soil surface. It therefore includes bits of plant roots from previous crops, leaves and twigs, bits of sawdust, the bodies of beetles, earthworms grubs and bugs, the remains of hordes of bacteria, fungi, living bodies of all these groups, chemicals such as enzymes, amino acids and antibiotics, that are either beneficial or harmful to microbes and plants and last but not least, the complex molecules that are collectively called humus.

Fermented food waste is pre-digested organic matter in the early stages of decomposition prior to completing the journey to become humus.