Influence of calcium fertilization on Douglas-fir foliar nutrition, soil nutrient availability, and sinuosity in coastal Washington

Sinuosity is a growth deformity affecting Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] and other conifers. Calcium is an important tree nutrient that affects the growth and stability of stems, which could cause sinuous growth. Much of the Ca stored in foliage may be bound as Ca-oxalate and no longer available for retranslocation. This study was conducted to determine whether Ca deficiency causes sinuous growth in coastal Washington. In early spring, six stands in southwest Washington were fertilized with Ca as lime or gypsum. Soil and foliar nutrients were examined before and after fertilization and partitioning of Ca within foliage was determined. Sinuosity and height were assessed at 0, 6, and 18 months after fertilization. Although gypsum application resulted in higher soil exchangeable Ca the lime treatment had the highest foliar Ca concentrations. Trees with higher foliar Ca concentrations led to higher water- (foliar membrane-associated), acetic acid- (Ca-pectate), and hydrochloric acid-extractable Ca (Ca-oxalate). Sinuosity was not decreased with Ca fertilization. The gypsum treatment had more sinuous growth in the first year after fertilization. Therefore, Ca fertilization increased soil and foliar Ca, but did not decrease sinuosity.