Use of an agro-industry treatment plant sludge on iceberg lettuce growth

Abstract

In the presented study, potential use of treatment plant sludge in agriculture is investigated. Sludge generated from an agro-industry (vegetable processing) is applied to pots at different loadings (0–100% sludge mixtures) for iceberg lettuce cultivation and the impacts of the sludge on plant growth are assessed by counting growing plants and leaves and weighing roots green and main parts of the plants. The least significant difference (LSD) method is used to test the significance of sludge loadings on plant growth. The conducted experimental data have shown that plant growth patterns have been influenced from the sludge loadings to a certain extent. In general, 25 and 50% of the sludge treatments have yielded lower plant growth due to nitrogen deficiency in raw sludge. On the other hand, high phosphorus content of sludge is replaced with nitrogen at high sludge loadings, thus maximum plant growth (both in green part and root weights) is obtained for the 75% sludge treatment (corresponding to 496 t/h sludge application). In addition, heavy metal concentrations have been measured in both leaves and roots and compared with the acceptable limits given for lettuce plant. Application of sludge did not significantly increase nickel, lead, cadmium, and manganese contents of lettuce plants. Consequently, results from pot experiments demonstrate that sludge taken from an agro-industry (vegetable processing factory) can be used as a partial substitute of chemical fertilizer and as a soil conditioner.