Heavy Metal Accumulation and Physiological Consequences in Selected Food Plants Grown on Sewage sludge Amended Soils PDF

Keywords

Food plants, Heavy metals, Liming, Nitrate reductase, Total soluble proteins, Sewage sludge.

Abstract

Pot experiments were conducted to explore concerns regarding agricultural use of sewage sludge for crop production. The extent of heavy metal accumulation and its subsequent impact on the physiological performance of six food plants grown on sludge mixed soils was explored. The effect of liming of sludge amended soil on the reduction of metal uptake by the raised plants was also tested. The contents of tested heavy metals were several times higher in pure sludge than in garden soil. Heavy metals were accumulated by plants cultivated on sludge mixed soil (SMS) or limed sludge mixed soil (LSMS) to levels significantly higher than those in control plants grown in garden soil (GS). The magnitude of accumulation was dependent on plant species and was generally higher in roots than in the shoot system. ALthough contents of all metals in tissues of SMS were significantly higher than those of GS plants, they were reduced by liming. No toxicity or deficiency symptoms were observed on SMS plants but contrary to expectations, cultivation of plants on SMS was generally enhancing to all tested physiological criteria in all tested plants. For example, plant growth, the end product of physiological performance, was improved by 30%, 40%, 25%, and 25% in Corchorus, Eruca, Raphanus and Spinacia respectively. Similar effects were recorded for chlorophyll content, activity of leaf nitrate reductase and total soluble proteins. Results are discussed from the viewpoint of the practicality of using sewage sludge in agriculture in the State of Qatar.