Other information also from England concerns the use of so-called
"minerals" which I prefer to call "essential inorganic nutrients," and
name by the element or the compound in which the element is contained.
"Minerals", strictly speaking, refers to compounds formed by nature as
rocks, ores, brines, salt deposits, etc.
Professor Wallace, Director of Britain's Long Ashton Research
Station[6], has laid the foundation for diagnosing mineral deficiencies
by leaf symptoms. These are reliable indicators of what nutrients to
furnish plants when they are distinct and easily recognized. But for
subacute deficiencies, plant analysis and injections are resorted to.
Injections of manganese sulphate as pellets into holes drilled in trunks
of cherry trees caused orchards that had been barren, to bear heavy
crops a few months later.
Manganese, boron, zinc, copper, iron, magnesium also lend themselves
quite readily for applications as nutritional sprays, when applied as
suitable compounds such as the sulphates. Both spray applications and
tree injections have great diagnostic values, because a response to
them, if needed is relatively quick. When trees are deficient their
foliage will show marked improvement from a spray application within a
few days, so that a test can be made on a few trees before an entire
orchard is treated. Trunk injections should of course be made during the
dormant season for results to show the following summer.