Determining air entry value in peat substrates

Insufficient aeration in artificial mixes used for nursery and greenhouse production is commonly reported to be a problem. To diagnose aeration problems, gas relative diffusivity estimates can be used. These estimates can be obtained indirectly from measurements of air entry value, saturated hydraulic conductivity and the water desorption curve. In here, a rapid tension chamber method for measuring air entry is proposed. To verify applicability of the method, different potted substrates were inserted into a tension chamber apparatus and water was extracted from the saturated substrate by establishing a contact with an unsaturated body located outside the chamber. The potential within the chamber was monitored over a 5-min period and the point of air entry was calculated thereafter. Statistically equal estimates of air entry were obtained with this technique compared with values derived from the tension table, for a wide range of air entry values in peat-based substrates.