successive generation lives
on what is left of the last in the soil plus what it adds from the air
and sunshine. As soon as a leaf or tree trunk falls to the ground it is
taken in charge by a wrecking crew composed of a myriad of microscopic
organisms who proceed to break it up into its component parts so these
can be used for building a new edifice. The process is called "rotting"
and the product, the black, gummy stuff of a fertile soil, is called
"humus." The plants, that is, the higher plants, are not able to live on
their own proteids as the animals are. But there are lower plants,
certain kinds of bacteria, that can break up the big complicated proteid
molecules into their component parts and reduce the nitrogen in them to
ammonia or ammonia-like compounds. Having done this they stop and turn
over the job to another set of bacteria to be carried through the next
step. For you must know that soil society is as complex and specialized
as that above ground and the tiniest bacterium would die rather than
violate the union rules. The second set of bacteria change the ammonia
over to nitrites and then a third set, the Amalgamated Union of Nitrate
Workers, steps in and completes the process of oxidation with an
efficiency that Ostwald might envy, for ninety-six per cent. of the
ammonia of the soil is converted into nitrates. But if the conditions
are not just right, if the food is insufficient or unwholesome or if
the air that circulates through the soil is contaminated with poison
gases, the bacteria go on a strike. The farmer, not seeing the thing
from the standpoint of the bacteria, says the soil is "sick" and he
proceeds to doctor it according to his own notion of what ails it. First
perhaps he tries running in strike breakers. He goes to one of the firms
that makes a business of supplying nitrogen-fixing bacteria from the
scabs or nodules of the clover roots and scatters these colonies over
the field. But if the living conditions remain bad the newcomers will
soon quit work too and the farmer loses his money. If he is wise, then,
he will remedy the conditions, putting a better ventilation system in
his soil perhaps or neutralizing the sourness by means of lime or
killing off the ameboid banditti that prey upon the peaceful bacteria
engaged in the nitrogen industry. It is not an easy job that the farmer
has in keeping billions of billions of subterranean servants contented
and working together, but if he does not succ