Growing Food: A Guide to Food Production

The Benefits of Humus
Humus, which consists of organic matter that has partially or fully decomposed,
improves the properties of all types of soil, in the following ways:

• protects soil from erosion by both water and wind;


• allows water to slowly and gently filter down through the soil, and reduces the run
  off and loss of water;


• improves light soils by increasing their water holding capacity, and other useful
  properties, while it improves heavy soils by giving them a “crumb” structure which
  is more easily cultivated (humus makes the soil become “lighter” ie more easily
  ploughed, cultivated);


• reduces water loss by evaporation from the soil;


• feeds earthworms and other beneficial insects;


• assists the soil to warm up more quickly in the spring, and to stay warm for longer
  in the winter;


• supplies essential nutrients to plants in a slow and gentle manner, and assists
  minerals in the soil to become more available to plants;


• reduces the speed of chemical changes when lime or inorganic fertilisers are added
  to the soil;


• releases organic acids which help to neutralise alkaline soils;


• “holds” nitrogen, in the form of ammonia and other compounds, so that the
  nitrogen is not denitrified by bacteria and so made unavailable to plants;


• reduces the damaging effects of fungal diseases and eelworms.

Maintenance of the Soil’s Organic Matter Content
It is easy to see from the list above that the maintenance or improvement of the soil
organic matter content is essential for satisfactory long term food production.
Unfortunately, in the presence of moisture, warmth and air, organic matter breaks
down—it oxidises—and disappears in the form of carbon dioxide and water, leaving a
small residue of minerals. This happens more rapidly in “hungry” soils—the light, sandy
ones - than in heavier and colder soils.
Therefore the organic matter in the soil has to be constantly replenished by adding to
it any form of organic material, such as manure, compost, green manure, leaf mould,
peat, seaweed, sawdust, human excreta, crop residues and roots, weeds, grass etc.

The Compost Heap—three heaps good, one heap not so good
If there is enough available space, the easiest way to produce compost is to make three
separate heaps, sited as close to each other as practical. The first heap is the one

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the soil particles open, which is desirable in heavy clay soils but less desirable in light
sandy soils. But with all types of soil the application of undecomposed organic matter

water.

does tend to reduce erosion and improve the capacity of the soil to retain nutrients and

Anything which has lived before can live again

Indeed -
!

GROWING FOOD – THE FOOD PRODUCTION HANDBOOK