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Variation in the Nitrogen, Phosphorus, and Potassium Contents of Pine Needles with Season, Crown Position, and Sample Treatment¹

ABSTRACT

Important variations occur in potassium, nitrogen, and phosphorus contents of first-year pine needle tissue depending on the part of the crown sampled, the time of year, and the tissue drying procedure. The primary aim of the study was to provide a basis for standardizing the sampling routine in collecting pine needles for foliar analyses. Several plantations in New York were systematically sampled and analyzed by standard chemical procedures to obtain data on the magnitude of these variations which have been observed by some workers, yet often ignored in tree nutrition studies. The data confirm previous observations of the percentagewise decline of potassium, nitrogen, and phosphorus in needle tissue from an early summer maximum to a fairly constant base level during the winter months. Late fall and winter sampling is recommended for foliar analysis of pine tissue. At this season, the needles are likely to be least affected by confounding physiological changes, and are also more expressive of soil fertility levels and species norms. Mid-crown positions are recommended as expressive of crown means, whereas aspect is not considered important. Stripping of needles from branches and immediate oven-drying (70°C.) after collection are necessary. Important dry weight losses in tissue which result in increases in nutrient percentages may occur in material which is allowed to air-dry.

¹ Presented before Div. V-A, Soil Science Society of America, Dallas, Tex., Nov. 19, 1953.

² Assistant Professor of Silviculture, State University of New York, College of Forestry. The author gratefully acknowledges the valuable counsel of Prof. S. O. Heiberg during all phases of this investigation. Credit is due Messrs. J. A. Hill and V. Kaufman of the N. Y. S. Conservation Department for most of the field collections. Dr. L. C. Walker and Messrs M. Steinberg and William Cowan assisted with the chemical analyses.

Received for publication December 14, 1953.