In California a manganese deficiency has been observed on English
Walnuts[10], and 5-15 lbs. commercial manganese sulphate was used per
100 gallons of water during late May, through June, to correct this.

Sprays should be applied at ten day intervals until the deficiency
symptoms no longer persist.

Plausible reasons for the somewhat quicker action of sprays than
fertilizers may be furnished by two prominent authorities:

McCollum[11], one of our foremost nutritionists, first noted the
discovery that the leaf of the plant is a complete food, and that none
of the storage organs of plants, seeds, tubers, roots, fruits enjoy that
distinction. In the leaf, biological processes are most active. It is
the site of synthesis of proteins, carbohydrates and fats. The leaf is
rich in actively functioning cells which contain everything necessary
for the metabolic processes, and they supply all the nutrients which an
animal requires. ("All flesh is grass").

Hoagland[12], another authority, writes on this subject thus:

"It is now certain that soils are not invariably capable of
supplying enough boron, zinc, copper and manganese to maintain
healthy growth of plants. This knowledge has come mainly during the
past ten years. Within this period thousands of cases from many
parts of the world have been reported of crop failure, of plant
disease, resulting from deficiencies of micro nutrient elements....
The statements do not imply that most soils are deficient in any of
these elements, but the areas involved are large and important
enough to warrant the view that the recognition of micro nutrient
deficiencies constitutes a development in applied plant nutrition
of major significance.

"When I refer to deficiencies of boron, copper, manganese, or zinc,
it is not a question of absolute deficiency in total quantity of
the element present in the soil, but rather a physiological
deficiency arising from the insufficient availability of the
element in the plant; in other words, not enough of the element
can be absorbed and distributed in the plant for its physiological
needs at each successive phase of growth."

Nutritional sprays under such circumstances may prove the remedy, and we
have experimental evidence to support this. Nut trees as is shown by the
above mentioned experiment, may respond to spray applications equally as
well as citrus, othe