PHYSICAL-PROPERTIES OF MEDIA FOR CONTAINER-GROWN CROPS .1. NEW-ZEALAND PEATS AND WOOD WASTES

Physical properties of New Zealand peats from 5 sources and of wood wastes, bark and sawdust were evaluated in relation to container-grown crops. For comparative purposes, Irish peat was included. All the peats had adequate air space (AS), but the Springhill peat and New Zealand Forest Service bark and sawdust had a particularly high AS (35-38%). Easily available water (EAW) was also adequate in all peats. New Zealand Forest Service bark and sawdust had inadequate easily available water (EAW, 10-12%), but grinding the bark increased this property. All the peats had similar water-buffering capacity (WBC) with the Irish peat having the highest value. The wood waste materials had inadequate WBC. Total porosity was generally adequate in all materials studied and was highest in Springhill peat. The bulk density (BD) was closely related to degree of decomposition (r = 0.95***) and also inversely related to AS and total porosity (r = -0.82* and r = -0.65, respectively). © 1979.