Mineral nutrition and growth of containerized Pinus halepensis seedlings under controlled-release fertilizer

Low, moderate and high rates (3, 5 and 7 g/l, respectively) of two controlled-release fertilizer (CRF) types, Osmocote 9-13-18 and Osmocote 17-10-10 were evaluated for their effects on production of containerized Pinus halepensis planting stock. Both formulations had similar patterns of nutrient release, with high release rates during the first 2-3 months, in contrast with minimum seedling uptake (determined by stem volume current increment). Shoot morphological attributes improved with increasing application rate regardless of formulation, though root growth was not affected. Shoot/root ratio was significantly affected by both factors, with the highest value (3.3 g/g) observed with Osmocote 17-10-10 at the 7 g/l rate. Needle N concentration was significantly affected by both rate and formulation, with 17-10-10 at the 7 g/l rate producing the highest value (18.5 mg/g). Needle P concentration was not affected by rate, and was low in all treatments (maximum of 2.2 mg/g), particularly in the 17-10-10 formulation, suggesting that P enrichment may be needed to improve its composition. Needle K concentration was significantly affected by rate, regardless of formulation. Absorption efficiency of N was near 40% in all treatments, although K and P recovery was lower. The CRF types used in this study may be useful for plant production of P. halepensis, promoting suitable morphological values and nutritional status. (C) 2004 Elsevier B.V. All rights reserved.