Potassium Fertilization Effects on the Bending Properties of Red Pine Wood

Wood samples were taken from 36-year-old red pine trees growing in two areas of a plantation on an outwash palin in the Pack Forest near Warrensburg, New York. The sites were identical except that one was deficient in potassium and the other had been fertilized by broadcast of potassium at 200 pounds per acre 20 years prior to sampling. Five dominant trees were sampled in each plot by cutting samples from internodes at comparative heights from the ground. Static bending tests were performed on twenty trees from each group. Force-deflection curves were plotted for each test; from these curves, modulus of elasticity, work to proportional limit, work to maximum load, modulus of rupture, and fiber stress to proportional limit were calculated. Data indicated that treatment with potassium fertilizer did affect the static bending properties of the wood. Modulus of elasticity was significantly increased, work to proportional limit and work to maximum load decreased, while modulus of rupture and fiber stress to proportional limit showed small changes. The over-all effect of treatment produced wood with properties similar to those of normal growth red pine, as compared to standard values in sources such as the Wood Handbook. For structural applications, the most significant results are increases in modulus of elasticity and fiber stress at proportional limit. These properties govern design stresses and load-deflection relations; increases could lead to more efficient utilization of the material in lumber or other wood-base structural material.

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