Use of sewage sludge as a greenhouse soil amendment. II. Influence on plant growth and constituents

Abstract

A greenhouse study was conducted to determine the effect of soils amended with sludge applications on the early growth of tomato seedlings ( Lycopersicon esculentum var. Homestead). Sewage sludge was mixed with the soil at rates of 0, 10, and 25% by volume. Prior to the sewage sludge additions, inorganic fertilizers were added to ensure adequate concentrations of all essential elements. Apical chlorosis appeared on tomato plants grown on soil treated with both 10 and 25% sewage sludge treatments within 4 weeks after transplanting. Plant height, green plant weight, dry weight, and dry weight per 1 cm in height were greatest on check treatments and equal for the 10 and 25% sludge treatments. Soil type had little effect on plant growth and the percentage of dry weight was not affected by sewage sludge rate or soil type. The cause of inhibited growth and chlorosis was probably due to excess Zn concentrations in the soil and plant tissue as a result of sewage sludge applications. The Zn concentration in the plants grown on the 10 and 25% sewage sludge treatments was approximately 25 times higher than the Zn concentration in the plants grown on the check treatment. It is also possible that the interaction of other heavy metals such as Mn, Cu, Cd, Cr, and Pb could have contributed to the inhibited growth and chlorosis.