It is furthermore safe to state at the present time that fertile soils
should contain at least the following twenty elements: Nitrogen,
phosphorus, potassium, calcium, magnesium, sulphur, hydrogen, carbon,
oxygen, iron, sodium, chlorine, aluminum, silicon, manganese, copper,
zinc, boron, iodine, and fluorine.
Until quite recently many scientists believed that only the first ten
elements were necessary for growth and maturing of crops; that only the
first three should be considered as fertilizer ingredients, and that the
others were supplied by soil, air and water, or were present as natural
fillers in manures and fertilizer raw materials.
The modern agronomist, however, takes all these twenty essential
elements into consideration, and many so-called "complete" fertilizers
contain at least sixteen to eighteen, if not all of the elements
mentioned above. Cobalt, essential to animal nutrition, can also most
economically be supplied through the soil, even though crops grow
without it.
As long as we have sufficient experimental research data that at least
nineteen elements are invariably essential to all life, it stands to
reason, that they at least must also be present in one way or another
for the normal, or better the optimum growth of nut trees, and a crop of
more nutritious nuts. Therefore, every time one of them is considered,
all the others must also be borne in mind. It will neither prove
difficult nor costly to experiment with them. It is a matter of finding
the proper balance of everything essential for optimum nut tree growing.
Indeed, to ascertain the true balance of all elements that are
invariably essential to life, and their relationship to the elements
which are variably essential, would quite naturally appear to constitute
the quintessence of research still to be performed. We cannot control
such essential factors as climate, weather, sunshine, but man can
control the supply and adjustment of nutrients to trees, and it rests
entirely with him to do so.
There is one advantage a nut crop has over some other crops; it does not
have to be harvested before fully mature. Nut crops obtain the benefit
from elements that may be slowly assimilated during the season.
The following experimental and historical evidence and opinions have
come to my attention, and I record them for what interest they may have.
Past experience is often discarded as too old, but many a time an
experimenter was ahead of his time, and his work remained unrecognized,
so that now some old references can be revived and presented as
novelties. What the past ignored may indeed be due to the ignorance of
those who did the ignoring.