Effect of Sludge Application on the Dry Matter Yield and Heavy- metal Content in Palak (Spinacia oleracea L.) in Three Sub-tropical Semi-arid Soils

摘要

A green-house experiment on three sub-tropical semi-arid soils was conducted to investigate the effect of different sludge types of coca-cola soft-drink industry viz. water treatment plant sludge (WTS), effluent treatment plant sludge (ETPS) and filter cake sludge (FCS) applied @ 1.0, 2.0 and 4.0 per cent (on dry weight basis) on dry matter yield (DMY) and heavy metal (Cd, Pb, Ni and Cr) content in Palak (Spinacia oleracea L). Sludge application @ 4.0 per cent represents loading of Cd, Pb, Ni and Cr@ 3000, 60400, 29800 and 29800 mug pot~(-1) through WTS, 6800, 98200, 89400 and 116200 mug pot~(-1) through ETPS and 240, 3600, 6600 and 5000 muq pot~(-1) through FCS. Averaged across the applied rates and soils, DMY of second palak crop was 74.4 per cent lower than the first crop. Significant increase in leaf Cd and Pb content of palak crop in Amritsar and Fatehgarh Sahib soils with ETPS @ 4.0 over 1.0 per cent applied level was obtained, in contrast to non-significant increase at same application rates in Ludhiana soil. Linear response of sludge application rate on increased heavy metal uptake from three sub-tropical semi-arid soils was observed for Cd, Pb and Ni, in contrast to Cr uptake that exhibited linear declining response to increased Cr loading rate through sludge. However, infinitesimally negligible contribution of individual sludge type, irrespective of the applied rate, towards total heavy metal uptake by palak crop from three soils was observed. The assessment of health risks associatedwith heavy-metals in the palak grown in soils amended with coca-cola bottling plant sludge, therefore recapitulates that palak should be consumed cautiously by human beings. The results revealed that soil acts as absorptive matrix for heavy-metals and affects their transformations and availability. All types of sludge be kept separately and be mixed only after getting them tested from a laboratory for their safe use.