Wetting Agent Addition for Limiting Risks of Hydrophobicity of Peat Substrate

An important constraint of peat substrates is their hydrophobic character which appears when they undergo a high degree of desiccation. The amount of time (and irrigation events) needed to rewet hydrophobic peat-based substrates is long and the quality/properties of the substrate can be decreased as a result. To remedy this, the use of wetting agents is already common practice and is known to improve the wettability of peat-based substrates. In order to avoid these negative impacts for plant growth, and then to improve irrigation management, this work aimed to estimate the wettability (by contact angle measurements) and hydration efficiency of a peat substrate, with or without wetting agent addition and prepared at different moisture contents: 25%, 37.5%, 50% and 62.5% (by weight). Results confirmed the positive effect of wetting agent addition on the wettability and hydration efficiency of peat. In details, its incorporation into peat did not reveal significant differences in wettability and hydration efficiency at higher water contents (i.e., when the materials are wetted and then hydrophilic), but subsequently led to a progressive increase in wettability and hydration efficiency for drier peat. So, wetting agent should be considered by its ability to improve the wettability of peat with a hydrophobic character, thus improving the ability and speed of the peat to be rewetted, rather than only their ability to influence the water retention characteristics of peat.