Relation of calcium and magnesium to the growth and quality of tobacco
McMurtrey, J.E. Jr.
When only nitrogen, phosphorus, and potassium are supplied in the fertilizer on some soils the growth of the tobacco plant exhibits definite pathological symptoms and growth is decidedly reduced. The addition of magnesium results in some increase in growth, but the growth still may be abnormal. This abnormality consists of development of upper leaves of the plant in which the tips and margins are partly missing. This gives these leaves a cut-out appearance. The plant as a whole shows a dark green color and in the later stages the terminal bud dies. This condition is corrected by the addition of calcium and may be considered as typical of calcium deficiency. The addition of calcium alone to the mixture supplying nitrogen, phosphorus, and potassium results in characteristic symptoms of magnesium hunger, which are typified by a breaking down of the chlorophyll. This chlorosis begins on the lower leaves of the plant and at the tips of the affected leaves. It appears that the leaf tissues should contain more than 1% of calcium to prevent symptoms of its shortage. The requirement for prevention of symptoms of magnesium deficiency is a content of around 0.25% in magnesium in the dry leaf. These requirements have been met by furnishing in suitable forms 35 pounds of calcium and 12 pounds of magnesium per acre on the soils in question. However, when dolomitic limestone was the source of magnesium it was necessary to supply considerably larger quantities. This material has not given satisfactory results with tobacco under all conditions. Where farm manure and other organic materials of plant or animal origin have been used extensively as fertilizers, a shortage of calcium and magnesium has not been apparent. The extensive use of superphosphate or other calcium phosphates as constituents of standard fertilizer mixtures has avoided any danger of loss of production from acute shortage of the element calcium.Show more [+] Less [-]