Effects of Sewage Sludge Application on Growth of Maize Grown in Aluminum-Toxic Soils

In the present study, a pot experiment was conducted to investigate the ameliorative effects of sewage sludge on maize grown in acid soils by measuring plant growth and physiological responses. The sewage sludge had higher pH and organic matter than red soil, thus the application of sewage sludge significantly increased soil pH and decreased monomeric aluminum (Al) concentration in soil solution. In general, there was a trend of increasing plant height, fresh weight, chlorophyll (Chi) content and activities of peroxides (POD) and catalase (CAT), or decreasing contents of malondialdehyde (MDA) and membrane permeability (MP), with sewage sludge ratio increased from 0% to 10%. However, those index mentioned above were opposite at a higher sewage sludge application ratio, ie. 30%, partly due to the high contents of soluble salts and NH₄-N in sewage sludge. The physiological amelioration (such as keeping higher activities of POD and CAT, more chlorophyll content and lower contents of MDA and MP) for maize grown in Al-toxic soils at 10% sewage sludge ratio provides foundations for the tolerance to Al, thus resulting in highest plant growth.