Growth and nutrition of containerized singleleaf pinyon seedlings in response to controlled release fertilization

Fertilization with four controlled release nutrient formulations, Sierra 17 -6-10, Sierrablen 18-7-10, High N 24-4-8, and Osmocote 18-6-12, was evaluat ed for its capacity to facilitate development of containerized singleleaf p inyon (Pinus monophylla Torr. & Frem.) planting stock. A water-soluble fert ilizer treatment using Peters 20-10-20 and nonfertilized seedlings provided for comparisons of nutrient amendment effects on growth and nutrition, and each fertilizer formulation was applied using low, medium, and high rates. After 24 months, the high application rate of the Peters formulation produ ced the largest seedlings overall. Among controlled release treatments, the Sierra formulation applied at the medium rate resulted in the greatest sho ot dimensions, although the low rare of this fertilizer. produced the great est combined shoot and root dry weight. All treatments resulted in low shoo t/root ratios with the exception of the high application rate of Sierra 17- 6-10. Overall, fertilized seedlings exhibited high foliar concentrations of N, P, and K but low concentrations of Ca, Mg, Fe, Mn, Zn, and B relative t o nonfertilized seedlings. Foliar S was low in all seedlings relative to do cumented standards for containerized conifers, while Cu was unaffected by t reatment. Among fertilized seedlings, moderately high N uptake coupled with high P generally resulted in the greatest stimulation of seedling growth. These results indicate that controlled release fertilization, a method part icularly well suited to smaller, less mechanized nurseries, can facilitate the production of containerized singleleaf pinyon with careful selection of nutrient formulation and application rate, but that a production period of similar to 2 years is required to grow planting stock with desired attribu tes.