583 Utilization of Zeolite as a Substrate for Containerized Oriental Spruce (Picea orientalis L. (Link.)) Seedlings Propagation S. Ayan Z. Yahyaoglu V. Gerçek and A. Şahin Gazi University Blacksea Technical University Eastern Blacksea Forestry Faculty Forestry Faculty Research Institute Kastamonu Trabzon Trabzon Turkey Turkey Turkey Keywords: oriental spruce, zeolite, growing media, seedling, morphological character Abstract This study was designed to investigate influence of different growing media and their mixtures (with zeolite and without zeolite) on seedling morphological character- istics of oriental spruce (Picea orientalis L. (Link.)). Eighteen growth media with different volume combinations (%) (7:3, 5:2:3, 6:2:2, 7:2:1, 5:2:2:1) of Barma peat (BP), tea residue compost (CTR), fine pumice (FP), coarse pumice (CP), perlite (P) and zeolite (Z) were prepared as a potting material, then sown with oriental spruce seeds. In this study, irrigation strategies were applied based on observation, and the same fertilization regime was applied to all the media. At the end of the second growing period, 30 seedlings from each treatment with three replications were harvested and measured for height (SH), root collar diameter (RCD), root dry weight (RDW), stem dry weight (SDW) and dry root percentage (DRP). As a result, significant difference was not determined among the treatments as to the SH, RCD, SDW/RDW and DRP. However, significant difference was determined among the growth media as to the RDW and SDW. The maximum SDW was determined for BP (0.5) + CTR (0.2) + CP (0.2) + Z (0.1) medium (3.24 g) while BP (0.6) + P (0.2) + Z (0.2) (1.59 g) medium showed minimum SDW. In addition, the maximum RDW were determined for BP (0.5) + CTR (0.2) + CP (0.2) + Z (0.1) medium (1.82 g) while BP (0.6) + CP (0.2) + Z (0.2) medium (1.01 g) showed minimum RDW. Addition of 20% zeolite to growing media types had a negative effect on the seedling morphological characteristics. Still, natural zeolite could be used as a substrate such as pumice and perlite: Turkey has 45.8 billions of zeolite potential. Therefore, using zeolite in nurseries may reduce the costs of nurseries. INTRODUCTION Peat has a long history of use in greenhouse production even though it is not a readily renewable resource. Low-quality degraded peat (≥ H 4 on the Von Post scale) which has small fibers holds larger amounts of water and less air as compare to less degraded peat (Allaire et al., 2005). Puustjärvi (1973) reported that the structure of peat may be too coarse or too fine. However, the most common problem with structure is that it is too fine. In that case, the water space becomes too large and the air space too small. In addition, the stability of physical properties of substrates is of primary concern for container-grown plants because changes in these properties may negatively affect plant growth (Allaire-Leung et al., 1999). Moreover, organic substrates as peat with low homogeneity and high decomposition ratio create pathological problems and cause toxicity (Koksaldi, 1999). Developing of peat alternative substrates is necessary for three different reasons: the resources of peat are limited; the pressure for using waste coming from human or industrial activities increases rapidly and the economic necessity to use locally produced waste products (Guerin et al., 2001). Substrates quality and stability are related to physical attributes such as particle-size and geometries, pore-size distribution, arrangement, which influence water and gas storage, and exchange properties (Allaire-Leung et al., 1999). The fertigation techniques normally used in container nurseries are not efficient for the management of nutrients. Moreover, control of substrate fertility potential is Proc. IS on Growing Media Ed.: J.-C. Michel Acta Hort. 779, ISHS 2008