Production et croissance des plants résineux dans différents substrats à base de compost dans une pépinière forestière moderne en Tunisie

Within the framework of the modernization of Tunisian forest nurseries, the substitution of forest or diversetextured agricultural soil-based substrates by compost produced from locally available forest biomass is one of the principal areas of research aimed at improving the quality of forest plants produced for reforestation programs. To develop a standard growing medium that could be used in these modern nurseries, and taking into account the availability of the diverse constituents, five compost-based growing media (S1, S2, S3, S4, and S5) mixed with different support and aeration materials were compared to a control substrate made of peat and vermiculite for the production of seedlings of three different forest species: Pinus pinea, Pinus halepensis and Cupressus sempervirens. Although the physical and chemical properties of the different growing media studied varied in their composition, by the end of the growing season these substrates had produced plants that complied with the quality standards required for Tunisian reforestation programs. Growth of the three species seedlings raised under nursery conditions in these substrates was significantly affected by the nature of the substrate used. Growth of plants produced using compost-based substrates was significantly lower than that achieved with other substrates. Our results clearly demonstrate that we are able to meet plant quality standards relating to growth while using substrates made up of local materials with no need to resort to the importation of peat and vermiculite. The adaptation and generalization of this approach in other countries with similar constraints offer promising prospects. Dans le cadre de la modernisation des pépinières forestières en Tunisie, la substitution des substrats à base de terreau forestier ou de sols agricoles par un compost produit à partir de la biomasse forestière localement disponible figure parmi les principaux axes de recherche en matière d’amélioration de la qualité des plants forestiers pour satisfaire les programmes de reboisement. Pour la mise au point d’un substrat standard utilisable dans ces pépinières, et tenant compte de la disponibilité des divers constituants, cinq substrats à base de compost mélangé à divers matériaux ont été comparés à un substrat témoin, constitué d’un mélange de tourbe et de vermiculite, pour la production de plants de trois essences forestières : Pinus pinea, Pinus halepensis et Cupressus sempervirens. Bien que les propriétés ph