Use of peat substitutes in growing media for Camellia japonica production

Peat is widely used in the ornamental nursery industry as major component for container plant production. Because of recent environmental concerns about peat extraction and the increase of its cost, the main objective of this study was to evaluate the suitability of five materials as partial peat substitutes for Camellia japonica ‘Hagoromo’ production. As alternative materials, local green compost, pumice, coconut fibres, coconut peat and pine barks were tested. A completely randomised greenhouse experiment was carried out from February 2005 to May 2007 in a commercial nursery devoted to producing acidophilus ornamental plants, located in Piedmont district (Northern Italy). There, the alternative substrates were compared with the standard one, in real production conditions. During cultivation, plant growth and flowering data were collected and subsequently subjected to statistical analyses. Overall, the tested peat substitutes performed as well as the standard substrate that could be replaced up to 30% without severe effects on growth or flowering. The pumice outperformed the other alternative materials for dry weight and SPAD values. The use of green compost caused an increase of weed development (particularly Marchantia polymorpha). In order to better evaluate the different substrates and to determine more precisely in which percentage the peat can be partially substituted, new experiments will be carried out in the period 2008- 2010.