Factors affecting zinc concentrations in plants grown in sludge‐amended soils

Abstract

Endive (Chicorium endiviaL.), a crop tolerant of acid soil conditions, was grown in a loamy sand, a loam, and a silt loam in a greenhouse. The soils were treated with limestone and a high‐calcium sewage sludge and with five levels of Zn ranging from 0 to 800 mg.kg^‐1. Limed soils were about pH 6 ‐ 6.5 compared to pH 4.5 ‐ 5 for unlimed soils. Zinc concentrations in shoots of endive grown in limed soils were less than those in unlimed soils. Sludge increased Zn concentrations in plants grown in the loam or silt loam but not in the loamy sand. The pH of the loamy sand was increased by the addition of sludge and may have limited Zn entry into the plants. A second addition of sludge enhanced Zn levels in plants, and the effects of the sludge appeared to be related to the resultant soil pH.