Municipal sewage sludge, aquatic weed compost on soil enzymatic activity and heavy metal accumulation in Kale (Brassica oleracea L.)

Enormous quantities of organic wastes such as sewage sludge (SS) and aquatic weed compost (AWC) are produced in large quantities on the banks of Dal Lake Kashmir. It is a challenging task for authorities to manage them properly. Therefore, the study's purpose was to evaluate these organic wastes agricultural use potential. The experiment was laid out in a randomized complete block design with three replications comprised of nine treatment combinations of SS, AWC and inorganic fertilizers. In the present study, the conjoint use of SS with chemical fertilizer recorded maximum build-up of soil microbial biomass carbon (MCB), urease and dehydrogenase activity with treatment T-1. There were significant correlations between soil MCB and from urease and dehydrogenase activity (r(2) = 0.95 and 0.97; P < 0.05), respectively. The micronutrient and heavy metal concentrations in kale exposed to SS and AWC were significantly higher than those in the untreated plants, with the highest concentration found in sole application of SS (T-7). However, heavy metal concentrations were within the acceptable limits and did not overcome the maximum phytotoxic levels. The study's finding leads to conclusion that SS along with chemical fertilizers (T-1) can improve the enzymatic activity in soil, quality parameters and nutrient content in plants thereby enhancing the yield.