PHYSICAL PROPERTIES OF PEAT SUBSTRATES IN AN EBB/FLOOD IRRIGATION SYSTEM
A coarse and a fine textured black peat, white peat and sphagnum peat showed optimal values in their physical characteristics directly affecting plant growth (air volume, easily available water, water buffer capacity and less readily available water) at the start of the experiment. The substrates were subjected to an ebb/flood irrigation system for 9 months and the changes of their physical properties in time were analyzed. Although there were no important changes in total pore space during the experimental period, important shifts in pore size distribution was observed. Both the mechanical action of rewetting and drying up (swelling and shrinking) and the biological activity (decomposition of the organic matter) were thought to be the reason. At least one of two statistical parameters that were used to describe the particle (aggregate) size distributions of the substrates decreased in time, indicating an aggregate breakdown over time. At the end of the experiment, the air volume of the fine textured substrates and the easily available water of the coarse textured substrates could not be considered as optimal. When using the substrates in an ebb/flood irrigation system, coarse textured substrates could be considered better than fine textured substrates since the loss in easily available water was compensated by the gain in water buffer capacity. It was only the coarse textured sphagnum peat that showed at all time optimal values in air volume and easily available water. This peat substrate appeared to be very suitable to be used in an ebb/flood irrigation system.
Michiels, P., Hartmann, R. and Coussens, C. (1993). PHYSICAL PROPERTIES OF PEAT SUBSTRATES IN AN EBB/FLOOD IRRIGATION SYSTEM. Acta Hortic. 342, 205-220
degradation, pore size distribution, moisture characteristic curve