Toxicity Assessment of Tannery Sludge Extract During Early Seedling Growth in Brassica nigra, Vigna radiata, Vigna mungo, Raphanus sativus and Capsicum frutescens

Tannery sludge (TS) contains a number of useful components like Organic carbon, Organic Matter, PO43-, Ca2+, Mg2+, and other nutrients essential for plant growth. However, presence of water-soluble toxic metals in TS may cause phytotoxicity. Primary objective of this work was to adopt a bio-chemical strategy for assessing the potential consequences of agricultural application of tannery sludge, via sludge characterization and subsequent bioassay investigations. Heavy metal concentration in the TS was found to be in the order of: Cr (19576±2065.52) > Pb (16.98±2.54) > Cu (1.76±0.20) > Ni (0.98±0.00) > Cd (0.19±0.00) mg kg-1. Further, bioassay tests were performed in terms of germination index (GI), relative seed germination (RSG) and relative root growth (RRG) on Brassica nigra, Vigna radiata, Vigna mungo, Raphanus sativus, and Capsicum frutescens. RSG and RRG were found to be more than 80% whereas, GI was > 66% in all the tested crops exposed to TS extract at 1:5 and 1:10 (w/v) dilutions. Results revealed that the toxicants present in the TS were failed to cause toxicity at early seedling growth and may be used as a soil conditioner after appropriate dilution. However, long term field trails are essential before agricultural utilization.