is as a distinct quality
over cane sugar. Manganese and other essential nutrients are known to
facilitate the production of proteins[19], and the question of better
quality nut production may well be examined from the viewpoint of the
indirect effect from activities of soil microbiology by manganese,
copper, cobalt and zinc. Some of these elements have also been classed
as inorganic plant hormones[20]. "Chlorosis," the yellowing of leaves,
may not only be a deficiency symptom of manganese, but also one of iron,
copper and magnesium. Lack of manganese can cause a decrease in
photosynthesis[21], so much so that in manganese deficient leaves the
CO2 assimilation may be reduced to half of normal. Herein, too, may lie
the cause of low yields, smaller roots and lowered resistance of those
roots to invading detrimental organism.

Contemporary work on soil microbiology may show that manganese and other
essential nutrients are perhaps most important in their functions for
the preservation and balancing of microbial life and actions in soils.
There is where tree nutrition must begin; whatever is neglected in soils
can at best only temporarily be adjusted afterwards. After all,
deficiency symptoms on foliage show lack of soil fertility, and while we
should welcome them for their diagnostic value, our corrective measures
to be most economical must be taken on soils.

Transmission of Inorganic Nutrients from Soils to Plants to Animals

Soil analysis and plant tissue tests both have their value, but also
their limitations. Many laboratories and experiment stations are
equipped to make rapid soil tests, and some engage in leaf analysis. It
is important that they be correctly interpreted. For instance, at the
Citrus Experiment Station, Riverside, California[22], bark and leaves
were collected from healthy and diseased Persian Walnuts. They were
analyzed for calcium, magnesium, inorganic phosphate, manganese and
iron. A higher percentage of ash was found in the diseased than in the
healthy bark, and calcium, magnesium, manganese and inorganic phosphates
were also generally higher.

It would be a fallacy I think to conclude therefrom that these elements
were not necessary, or were present to excess. They were probably
present because they had failed to function properly, due to changes in
weather, excessive rains or droughts, and could not eliminate
themselves.

We must consider the results from the functions of the essential
ele