Agriculture Reference
In-Depth Information
Chapter 7
Organic Matter
STEP 2
Despite some claims, plants and microbes really do care about the source of their nutri-
ents. They prefer and often do better with organic forms of the elements instead of synthet-
ic chemical forms. They prefer compost to synthetic nitrogen. While I definitely recom-
mend using products such as lime in certain circumstances, the thing most of us need to do
before all of that is start a regimen of deliberately increasing the organic matter content of
our soil. We can do this with leaves, compost and other organic materials, even cover
crops. After we've removed the threats and determined how we'll supply water to the
whole garden, we can start increasing the organic matter content of our soil.
In the last century, we've burned up more than 90% of the organic matter in many of our
soils through tilling, applying chemicals, and clearing plant residue without allowing or-
ganic matter to decompose. Humus is our ultimate goal, but we also want a supply of fresh
organic residue as food and shelter for microbes and animals. As this residue is broken
down, carbon dioxide becomes available to plants. Conventional agriculture has largely ig-
nored organic matter, and organic gardeners have relied on it perhaps too much at the ex-
pense of other management practices. Still, increasing organic matter and humus should be
one of our most important goals.
Humus, made up of biologically active complex carbon chains, is critically important in
the soil. While the term is often used interchangeably with organic matter, it's really organ-
ic matter that has been broken down by multiple organisms to the point where it won't get
broken down much more. Humus holds nutrients in the soil, including the fertilizers we ap-
ply. According to some, it particularly holds calcium, which otherwise likes to sink down
in the soil profile below most of the other minerals. It definitely holds water. Walk into
your garden in the middle of a rainless summer night and your shoes may very well get
soaking wet, if you have enough humus in your soil. It has many other important functions,
such as tying up toxins, contributing to better soil structure, moderating soil temperatures
and stimulating microbes.
