Apricot, sweet cherry, lemon, onions, peanut, soybean (two illustrations), tobacco (4 illustrations), sugarbeets, walnuts, wheat, all by different authors.
Manganese deficiencies in Indiana on soyabeans, hemp, corn, by courtesy of George H. Enfield, Purdue University.
Manganese on beets (mangels), (4 illustrations), and Romaine lettuce, Nassau County, Long Island. Courtesy of Dr. H. C. Thompson, Cornell University.
Many more are published in "Hunger Signs of Crops," an illustrated reference book popular with scientific farmers and growers[13].
Other deficiencies that have been observed on nut trees are the so-called "little leaf" or "rosette" of pecans and black walnuts[14], which is due to a lack of zinc. Strangely enough, healthy orchards in this case contained a preponderance of fungi, whereas in affected orchards the soil microflora was predominantly bacterial[15].
We now have definite experimental evidence that lime, manganese and zinc are required in appreciable quantities for the growth, health and bearing quality of nut trees. It is well to make sure of these elements in the soils devoted to nut tree planting, but it cannot be emphasized too often that all essential elements and factors should be taken care of; anyone of them may be the limiting factor in crop failure; the one that is absent is always the most important.
In regard to inorganic nutrients, more attention has probably been devoted to citrus trees than to any other tree species, largely because the soils of Florida and California require additions thereof. It would be unfair to say that such main fruit crops as apples, cherries, peaches, plums have been neglected; we merely possess more information on the nutrients of citrus trees than on other tree crops, as far as the micro essential nutrients are concerned. Most orchards and groves are fertilized only with nitrogen, phosphorus and potash, and limed when necessary. Nitrogen can stimulate size of fruit at the expense of quality.
A paper by P. W. Rohrbaugh[16], Plant Physiologist of the California Fruit Growers Exchange, Ontario, California, deals with eleven mineral nutrient deficiencies and their causes, viz: calcium, magnesium, potash, phosphorus, sulphur, nitrogen, iron, boron, zinc, manganese, copper, and this might well be used as a guide for nut trees.
6) Miscellaneous
A few oddities may also be mentioned for anyone inclined to experiment: