REUTILIZATION OF COAL FLY-ASH AND SEWAGE-SLUDGE AS AN ARTIFICIAL SOIL-MIX - EFFECTS OF PREINCUBATION ON SOIL PHYSICOCHEMICAL PROPERTIES

An experiment was performed to evaluate the importance of pre-incubati on on the stabilization of a soil-mix composed of coal fly-ash and sew age sludge. Sludge was amended with ash at rates of 0, 5, 10, 35 and 5 0% (w/w). Each ash-sludge mixture was mixed with a loamy soil at eithe r 1:1 or 1:5 ash-sludge mixture:soil (v/v) and then incubated under gr eenhouse conditions for 42 days. Ash amendment resulted in a decrease in EC, NH4+, PO43- and Zn, but an increase in pH and B for most of the incubation period especially for soil with 35 and 50% ash-sludge mixt ure added at 1:1 (v/v). Ammonium increased and then decreased while PO 43- and NO3- remained relatively unchanged, in the first 14-21 days an d then increased until the end of the incubation period. Soluble Cu of all treatments decreased at the end of incubation except for soil wit h 0% ash-sludge mixture at 1:5 v/v. With an increase in ash amendment rate, both seed germination and root growth of Agropyron elongatum in the soil extracts increased at each incubation period indicating the b eneficial effect of the fly-ash-sludge mixture. However; an incubation period of 21 days would be needed to obtain an optimum physico-chemic al condition for plant growth. (C) 1997 Elsevier Science Ltd.