Behaviour of Natural Wetting Agents by Plant Extracts on Peat-Based Substrates

Wetting agents or surfactants are used by substrate industries in order to reduce the surface tension of water, improving the speed of wetting and retention of water. These products can be divided into three groups: mineral, synthetic and natural additives. Regarding the first two groups, their behaviour and effectiveness are widely known whereas there is little information on natural organic additives. The aim of this work was to investigate efficacy, longevity and phytotoxicity of different surfactants obtained from plant extracts, in order to consider their possible use in the preparation of pot plant media, mainly for organic horticulture. Laboratory tests on different plant extracts were carried out to evaluate their influence on speed of wetting, wettability, capillary uptake, phytotoxicity and longevity. The results showed great variability in terms of effectiveness among the different plant extracts. Extracts from Plantago indica, and Althaea officinalis were the most interesting and reliable wetting agents. The Althaea officinalis extract improved all the parameters studied; it seems to be an interesting alternative to the synthetic materials in terms of wettability, capillary absorption, longevity and safety.