Sewage sludge amendment affects spinach yield, heavy metal bioaccumulation, and soil pollution indexes

Abstract

Use of sewage sludge (SS) in crop production is a feasible strategy for its disposal; however, its application may pose an adverse impact on soil and human health. Therefore, identification of the permissible level of SS is essential to prevent soil contamination. This research not only evaluated the impact of SS application on spinach (Spinacia oleracea L.) biomass yield but also tracked the accumulation of heavy metals in soil and plants. A pot experiment was conducted on Inceptisol with different levels of SS (0, 5, 10, 15, 20, 25, 30, 35, and 40 t ha−1) with recommended dose of fertilizers (RDF). The applications of SS at 20 t ha−1 resulted in the highest biomass yield; however, the concentration of zinc (Zn) and cadmium (Cd) has exceeded the safe limit in leaves. Heavy metal accumulation in the plant was the highest in SS at 40 t ha−1. Spinach grown at 20 t ha−1 and higher dose of SS exceeded the safe limit of Zn and Cd concentration in leaves, and the translocation factor (TF) of lead (Pb) and Cd was found to be > 1. The hazard quotient (HQ) of Pb > 1 at higher doses of SS indicates health hazard if spinach is used for consumption. Assessment of health risk showed that there was a possibility of Pb hazard at a high dose of SS (HI > 1). Evaluation of various soil pollution indexes revealed that the addition of SS enhanced the buildup of Cd and chromium (Cr) in soil. This study advocated the use of SS at 10 t ha−1 to sustain soil quality with no risk of food chain contamination.