always has a carbon to nitrogen ratio of from 10:1 to about 12:1,
just like compost from Garden "B." Garden writers call great compost
like this, "stable humus," because it is slow to decompose. Its
presence in soil steadily feeds a healthy ecology of microorganisms
important to plant health, and whose activity accelerates release of
plant nutrients from undecomposed rock particles. Humus is also
fertilizer because its gradual decomposition provides mineral
nutrients that make plants grow. The most important of these
nutrients is nitrate nitrogen, thus soil scientists may call humus
decomposition "nitrification."

When organic material with a C/N below 12:1 is mixed into soil its
breakdown is very rapid. Because it contains more nitrogen than
stable humus does, nitrogen is rapidly released to feed the plants
and soil life. Along with nitrogen comes other plant nutrients. This
accelerated nitrification continues until the remaining nitrogen
balances with the remaining carbon at a ratio of about 12:1. Then
the soil returns to equilibrium. The lower the C/N the more rapid
the release, and the more violent the reaction in the soil. Most low
C/N organic materials, like seed meal or chicken manure, rapidly
release nutrients for a month or two before stabilizing. What has
been described here is fertilizer.

When organic material with a C/N higher than 12:1 is tilled into
soil, soil animals and microorganisms find themselves with an
unsurpassed carbohydrate banquet. Just as in a compost heap, within
days bacteria and fungi can multiply to match any food supply. But
to construct their bodies these microorganisms need the same
nutrients that plants need to grow--nitrogen, potassium, phosphorus,
calcium, magnesium, etc. There are never enough of these nutrients