Growth performance, metal accumulation and biochemical responses of Palak (Beta vulgaris L. var. Allgreen H-1) grown on soil amended with sewage sludge-fly ash mixtures

Agricultural utilization of sewage sludge (SS) and fly ash (FA) has become both, a common practice and an alternative disposal method for these wastes all around the world. The present study was conducted to assess the effect and viability of co-application of SS and FA (SLASH) in four mixing ratios denoted as A [4 (SS): 1(FA)], B [4 (SS): 2 (FA)], C [4 (SS): 3 (FA)] and D [4 (SS): 4(FA)] at three application rates viz. 20, 40 and 60% (w/w) with agricultural soil on biochemical, physiological and growth response of Palak (Beta vulgaris L. var. Allgreen H-1), a commonly used green leafy vegetable. SLASH amendment modified the physico-chemical properties of soil and increased the concentration of heavy metals (Cd, Cr, Cu, Fe, Ni, Pb, Zn) in soil and plant parts however, within the Indian permissible limit except for Cr, Cd and Zn in shoot. Experimental results revealed decrease in morphological and growth parameters such as root and shoot length, leaf area, root, shoot biomass etc. Lipid peroxidation, ascorbic acid, proline and protein content increased however, total chlorophyll and carotenoid content decreased indicating towards heavy metal stress induced biochemical and physiological response in Palak plants. Significant increase in yield was seen in some of the treatments viz. three mixing ratios B, C and D, with maximum increment shown by mixture D at 20 and 40% amendment rate. The results of this study suggest that though SLASH amendment for growing Palak improved the physico-chemical properties of soil amended and also the yield of the plants in some treatments, it may not be a good option due to risk of contamination of heavy metals such as Cr, Cd and Zn showing higher accumulation.