Abstract
Soil contamination with heavy metals caused by various industrial activities is a threatening global environmental issue of the current era. Chromium (Cr) is the most toxic heavy metal used in leather industry and disposal of untreated wastewater into natural water bodies leads to contamination of natural soil and water resources. We studied the combined effect of biochar and compost on improving the tolerance to Cr toxicity by enhancing the morpho-physiological and biochemical attributes of two maize cultivars (P-1543 and NK-8441) grown in tannery waste polluted soils. The results of this study reveal that Cr toxicity reduced the plant growth by affecting physiological and biochemical attributes. Here, compost and biochar application significantly increased the plant biomass (fresh and dry), height, photosynthesis, chlorophyll content, water relation, starch, and protein content over treatment set as control. However, significant decline in electrolyte leakage (EL), proline, lipid peroxidation, soluble sugars, and antioxidant enzymes (APX, GPX, GR, GST, GSH, SOD, and CAT) was observed by combined application of compost and biochar. Hexavalent chromium concentration was maximum decreased to 4.1 mu g g(-1) in soil after post-harvesting of maize cultivar NK-8441, while in roots and shoots to 22.6 and 19.2 mu g g(-1) of maize cultivar P-1543, respectively, by combined application of compost and biochar. Moreover, these both amendments in combination showed considerably better results than their sole application and cultivar P-1543 comparatively performed better than NK 8441, in both K and S soils. Correlation and principal component analysis (PCA) revealed mostly highly positive associations among all the studied morpho, physio, and biochemical attributes of maize plant with the few exceptions, particularly concentration of Cr(III) and Cr(VI) in soil. The present work concluded that combined use of biochar and compost has great potential to decrease Cr toxicity and improve plant growth in tannery polluted soils.