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Magnesium Deficiency of Some Northeastern Pines¹

ABSTRACT

Magnesium deficiency of Pinus resinosa, P. strobus and P. banksiana was studied in young forest plantations on light textured soils bordering the western and southwestern margins of the Adirondack province of New York.

The most conspicuous symptom of deficiency was a bright yellow discoloration of the tips of the current season's needles, appearing in the fall and affecting the upper part of the tree most strongly. When the deficiency was severe the chlorosis was followed by death of the needle tips or premature loss of foliage. Gross reductions in shoot growth and needle length occurred only under extreme deficiency or when lack of magnesium was accompanied by potassium deficiency.

In P. resinosa the appearance of deficiency symptoms was usually associated with magnesium contents less than .16% of the oven dry weight of mature first year foliage; with less than about .13% symptoms were severe. Fertilization with magnesium sulfate at rates of 20 to 50 lbs. Mg/acre eliminated or reduced the symptoms after a lapse of at least a year.

Fertilization of deficient trees with magnesium sulfate resulted in increased height growth over a period of at least three years. In two instances this increase was shown to be additive to that due to potassium, without evidence of significant interaction.

¹ Presented before Division V-A, Soil Science Society of America, Cincinnati, Ohio, Nov. 20, 1952.

² Department of Agronomy, Cornell University, Ithaca, N. Y. It is a pleasure to acknowledge the assistance of A. J. Woodford and F. E. Jadwin, District Foresters of the New York State Conservation Department, and their staffs in the conduct of the field work reported.

Received for publication December 6, 1952.