Production of containerized Jeffrey pine planting stock for harsh sites: Growth and nutrition as influenced by controlled-release fertilization

Low, medium, and high rates of four controlled-release nutrient amendments, Sierra 17-6-10, Sierrablen 18-7-10, High N 24-4-8, and Osmocote 18-6-12, were evaluated for their effect on production of containerized Jeffrey pine (Pinus jeffreyi) planting stock. Peters 20-10-20 water soluble fertilizer treatments and nonfertilized seedlings provided for comparisons of amendment formulation effects on growth and nutrition. In general, growth increased with increasing amendment application rates regardless of formulation. Seedlings fertilized with Peters 20-10-20 had the greatest shoot growth, although those that received Sierra 17-6-10 or High N 24-4-8 were only marginally smaller. The Sierra formulation proved most effective in the stimulation of root growth. Shoot/root ratios rose with amendment application rates, although all treatments produced proportional shoot and root mass. Fertilized seedlings had higher foliar N, P, and S concentrations, while K, Ca, Mg, Mn, and B concentrations were higher in nonfertilized seedlings. It is likely that N, P, and S nutrition contributed heavily to the variation in shoot and root growth among treatments. The aridity of the western Great Basin and eastern Sierra Nevada renders the regeneration of forests and woodlands difficult, but with careful selection of formulation and application rate, controlled-release fertilization may facilitate the production of container stock with the large caliper and balanced shoot and root growth necessary for successful field establishment on the harsh sites of this region.