The Growth of Corn Plant in Coal Fly-Ash and Lime-Stabilized Sewage Sludge

Abstract

A greenhouse experiment was conducted to compare the effects of fly-ash and lime amendments to sewage sludge on the growth and chemical composition of corn. Sludge was amended with fly-ash or lime at an application rate of 0, 5, 10, 20 and 40 % (w/w). Each of these mixture was then (1:4)-mixed with loamy soil (v/v). According to experiment results, the highest dry weight yields were obtained at sludge-soil mixture alone. Increasing fly-ash and lime amendment rates significantly decreased corn yield. With increasing coal fly-ash amendment rate, contents of N, P, Pe, Mn and Zn in plant tissues of corn decreased significantly, but Cd contents of shoots and roots increased markedly. Addition of lime-amendment sludge to soil generally decreased contents of N, P, Fe, Cd, Pb and Zn in shoot tissue. However, the shoot contents of N, Fe, Mn, Cd and Cu elevated considerably, at 40 % lime amendment rate. The high Cd Content of coal fly-ash caused increase in plant and soil Cd. The Cd, Cr, Cu and Pb contents of root tissue were significantly higher than those of the shoot tissue. Increasing fly-ash and lime amendment rates significantly increased soil pH. DTPA-extractable Fe, Mn and Ph contents decreased with an increase in fly-ash amendment rates, Lime stabilization of sewage sludge reduced DTPA Cd, Cu, Ph and Zn contents markedly, but Fe, Mn and Cr showed little changes. Therefore, the lime-stabilized sludge was more effective in decreasing heavy metal accumulation of plant and soil, compared to fly-ash. Addition of 10% lime amendment significantly reduced the availability or heavy metals without serious yield reduction of corn.