The results of applying three doses of coated slow release fertilizers OSMOCOTE 9-13-18 (1.5; 3.25 and 5 g/l) and OSMOCOTE 16-8-9 (3.25; 5 and 7 g/l) in producing Pinus halepensis seedlings are evaluated. Mixing the fertilizer in the growing media increased the salinity, but didn’t affect the germination and survival of the seedlings. N and P leach concentrations were correlated with the application rates, but K wasn’t. N, P and K shoot concentrations at lifting were correlated with the doses applied, although the relationship between K and doses was the weakest. Shoot growth responded significantly only to N doses. The relative N proportion in OSMOCOTE 9-13-18 was deficient, and OSMOCOTE 16-8-9 had a K deficient ratio, due to the dilution effect observed. The mineral nutrient uptake efficiency decreased in response to the dosis, but was higher than observed in liquid fertilizer injection methods.