553 Evaluation of Some Peat-Alternative Substrates in Horticultural Crops A. Lanzi, L. Incrocci a , R. Pulizzi and A. Pardossi Dip. Biologia delle Piante Agrarie University of Pisa Viale delle Piagge 23 56124 Pisa Italy P. Marzialetti Centro Sperimentale per il Vivaismo Via Ciliegiole 99 51100 Pistoia Italy Keywords: bedding plants, coconut coir fibre, compost, geranium, ornamental plants Abstract The price of peat, one of the most important constituents of growing media in pot plant industry (at least in Europe), is increasing and there is an emergent interest on peat-lands for their natural and/or archaeological value. This has produced an 'anti-peat' campaign in many European countries and is expected to lead, in the near future, to a drastic reduction in the use of peat in favour of alternative materials. The paper reports the results of three simple experiments performed to test two peat substitutes in growing media for outdoor or greenhouse container plants: coconut coir fibre and organic green compost (two commercial products from green and urban organic wastes were evaluated). In the first experiment, two shrubs (Photinia x fraseri ‘Red Robin’ and Viburnum tinus L.) were grown in four different mixtures: peat-pumice (1:1, v:v; standard substrate), pumice-coconut coir (1:1, v:v), pumice-compost-peat (0.50:0.30:0.20, v:v) and pumice-compost-coconut (0.50:0.30:0.20, v:v). In Photinia leaf area and/or the dry weight of whole plant and its main organs were significantly reduced when the pots were filled with substrates other than the standard one. By contrast, in Viburnum plant growth was stimulated by the use of alternative substrates. In the second and third experiment, other four different substrates were tested for greenhouse production of pot geranium (Pelargonium peltatum L.) or tray plugs of two bedding species (Calendula officinalis L. and Ageratum houstonianum L.) and tomato (Solanum lycopersicum L.): peat-perlite (0.75:0.25, v:v), coconut:perlite (075:0.25, v:v), compost-peat-perlite (0.375:0.375:0.250, v:v) and compost-perlite (0.75:0.25, v:v). In these experiments, compost was provided by a different supplier with quality certification and no important effect of growing medium on plant growth characteristics or seedlings emergence (exp. 3) was observed. These findings confirmed that compost and coconut coir may contribute to reduce, at least partially, the use of peat in professional horticulture, provided the producers have a well established form of quality assurance to ensure the consistency and safety of the product, which starts with strict selection of raw materials. INTRODUCTION The price of peat, one of the most important constituents of growing media in pot plant industry (at least in Europe), is increasing and there is an emergent interest on peat- lands for their natural and/or archaeological value (Armstrong, 2007; Rivière et al., 2008). This has produced an 'anti-peat' campaign in many European countries and is expected to lead, in the near future, to a drastic reduction of the employment of peat in favour of alternative materials. Two major candidates to replace, at least partially, peat in horticultural substrates are coconut coir and organic green compost. Coconut coir is a by-product of coconut (Cocos nocifera L.) industry located primarily in Sri Lanka, the Philippines, India and West Africa (Noguera et al., 2000). Coconut coir is a valuable substrate due to its buffering capacity and suitable ratio between aeration and water holding capacity; moreover, it does not decay rapidly, thus a incrocci @agr.unipi.it Proc. IS on Prot. Cult. Mild Winter Climate Eds.: Y. Tüzel et al. Acta Hort. 807, ISHS 2009