Abstract
THE occurrence of magnesium deficiency of fruit trees growing in the field has been recognized only in recent years. L. Southwick (Proc. Amer. Soc. Hort. Sci., 42, 85; 1943) describes a leaf blotch of apples which appears as an edge burn or interveinal necrosis, together with in some varieties a yellow banding or mottling of the leaves, appearing first in the older leaves and associated with a low magnesium content of the leaves, the scorched leaves usually containing less than 0·25 per cent magnesium. In the same journal D. Boynton, J. C. Cain and O. C. Compton report that seasonal variations in the potash and magnesium content of apple leaves agree with the seasonal differences in the incidence of leaf scorch and leaf blotch respectively. Leaf blotch due to magnesium deficiency may be reduced by soil application of magnesium sulphate, while it is aggravated by chloride of potash dressings (ibid., 42, 95; 1943). L. Southwick and J. K. Shaw find that spraying with magnesium sulphate solution (16 lb. per 100 gallon) gave a partial control of the magnesium deficiency leaf blotch, and that most magnesium-containing substances applied to the soil were effective but magnesium limestone was ineffective in curing the trouble.
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Magnesium Deficiency of Fruit Trees. Nature 155, 151 (1945). https://doi.org/10.1038/155151b0
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DOI: https://doi.org/10.1038/155151b0