In this range a decrease of more than three orders of magnitude in the unsaturated hydraulic conductivity was observed for peat. Results showed that sharp variations in hydraulic conductivity occur in a very narrow suction range (0–2.5 kPa). Model predictions of unsaturated hydraulic conductivity were validated by direct measurements. Measured water retention and saturated hydraulic conductivity data were used to estimate model parameters by a nonlinear least-squares curve-fitting technique. A predictive mathematical model was used to calculate the unsaturated hydraulic conductivity of the media. Water characteristic curves (drying and wetting cycles) and saturated hydraulic conductivity were measured. Tuff (granulated volcanic ash) and its mix with peat were also tested for comparison. The objectives of this research were to determine the hydraulic properties of sphagnum peat moss and to evaluate their potential effects on water availability. Transient changes in unsaturated hydraulic conductivity may result in reduced water uptake by plant roots.

We hypothise that the coarse structure of peat moss as well as of other container media may result in a sharp decrease in hydraulic conductivity, as the water content of peat is reduced. This approach is challenged in the present paper. Water availability to plants grown in containers is usually being evaluated using criteria based exclusively on water characteristic curves of the medium in which the plant is grown. The potential rate of water and nutrient supply to plant roots depends on the hydraulic properties of the container medium (growth medium, substrate), primarily on its unsaturated hydraulic conductivity, which is a measure of the medium's resistance to water flow.

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