Response of Douglas-fir and Western Hemlock Seedlings to Lime

Pot tests of lime and phosphate fertilizer on Arta, a low-base forest soil from the Washington coastal area, showed markedly increased growth of Douglas-fir from lime applications at 4,500 and 22,500 kg/ha. The high lime rate caused significant reduction in western hemlock growth. Phosphorus had no significant effect on growth of plants either alone or, except for weight of foliage, in combination with lime. Lime increased the N, Ca, and Mg content of Douglas-fir foliage but reduced levels of Mn and Al. Effects on hemlock were similar except that high lime reduced K and Mg. Also, hemlock foliage contained significantly more calcium and other cations than Douglas-fir. The relative importance of reduced uptake of Al and Mn and increased supply of Ca to the lime response by Douglas-fir is not known. Increased availability and uptake of N from liming was demonstrated but the importance for field conditions must be verified. The adverse reaction of hemlock to high lime may have resulted, at least in part, from high nitrate levels in the soil. Forest Sci. 19:220-224.