er crops can be brought about by greater
application of essential nutrients to soils or as nutritional sprays
direct to trees, and that such practices also reflect true economics.
The same principle should govern wood production.

According to our today's knowledge, there are at least nineteen elements
invariably essential to life, viz:

Primary: Hydrogen, carbon, nitrogen, oxygen, phosphorus.

Secondary: Calcium, magnesium, sodium, potassium, iron, sulphur,
chlorine.

Micro: Manganese, copper, boron, silicon, aluminum, fluorine, iodine.

Then there are another eighteen elements at least variably necessary to
life, viz:

(1) Variable Secondary Elements: Zinc, titanium, vanadium and bromine.

(2) Variable Micro-Elements: Lithium, rubidium, caesium, silver,
beryllium, strontium, cadmium, germanium, tin, lead, arsenic, chromium,
cobalt and nickel.

Elements in Soils Essential for Plant Growth

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 opt