A laboratory method for measuring physical properties of growing media and their evolution during drying/wetting cycles: preliminary results

Abstract : A new apparatus was developed for simultaneously and continuously measuring the water retention and shrink/swell properties of growing media during several drying/wetting cycles. Initial results obtained on peats show that water retention and shrink/swell properties are mainly affected by the first drying and rewetting cycle and remain quasi-constant thereafter, regardless of the intensity and the number of drying/wetting cycles. Hysteresis phenomena in water retention are always observed. The use of a wetting agent (as compared with water) in peat leads to the reinforcement of the physical stability of growing media and to the limitation of hysteresis phenomena in water retention for the highest suction values.