Urea fertilization and foliar nutrient composition of western hemlock ( Tsuga heterophylla (Raf.) Sarc.)

Foliar mineral contents of hemlock stands in coastal and Cascade Mountain zones of the Pacific Northwest were studied to determine the effect of urea fertilization on foliar nutrients. The results demonstrate that mineral concentrations vary among foliage age classes, stands, and zones. Concentrations of N, P, K, Ca, Mg, Al, Mn, Fe, Cu, Zn and B were significantly higher in the Cascade Mountain stands than in the coastal stands. Urea fertilization significantly increased the N content in all age classes of foliage but reduced the concentrations of P, Ca, Mg, Mn, Fe, Al and B, especially in coastal stands. The poor response of coastal stands to urea fertilization, therefore, is probably due to further reduction in already low foliar levels of essential nutrients other than N.