USE OF SEVERAL ORGANIC WASTE MATERIALS AS GROWING MEDIA FOR CONIFER PLANTS

In this experiment the use of different organic waste materials - poplar tree bark, palm fibre and sewage sludge compost (biosolid) - as substrates in the production of ornamental plants was studied, with a special interest in the suitability of palm fibre as growing substrate for conifer plants. the plant species tested were pinus densiflora, cupressus arizonica and c. sempervirens and the substrate mixtures were: (1) poplar tree bark, (2) poplar tree bark with 15% of sewage sludge compost, (3) poplar tree bark with 30% of sewage sludge compost, (4) palm fibre, (5) palm fibre with 15% of sewage sludge compost and (6) palm fibre with 30% of sewage sludge compost. the substrates were physically and chemically well characterized and 75-cm plants were grown on them for one year. for each species, the experimental design consisted of six random blocks with 60 plants per substrate grown in 7-i capacity pots. the plant and substrate status were periodically tested during the experiment. since biosolid recycling is the main objective of the present work, mixtures with 30% of composted sewage sludge will be the most convenient substrate to use. plant growth in palm fibre substrates mixed with biosolid showed similar results as those grown in poplar tree bark based substrates. for c. sempervirens and c. arizonica, a mixture of poplar tree bark or palm fibre and 30% biosolid compost in volume gave the best results. however, the lower cost of the poplar tree bark than the palm fibre substrate indicated the use of the pb+30% css. also, the results showed that palm fibre substrate alone was not a good growing media for cupressus plants.