Application of biosolid for berseem clover fertilization: Fodder characteristics and health risk assessment

Finding sustainable methods for utilizing biosolids, also known as municipal sewage sludge (SS), presents a pressing challenge in modern waste management practices. Therefore, this study aimed to evaluate the impact of SS amendment on growth, biochemical, proximate, and heavy metal bioaccumulation parameters of berseem clover ( Trifolium alexandrinum L.) fodder crop under field conditions. Trifolium alexandrinum was cultivated using different rates of SS mixing (i.e., T0: 0% as control with no SS application, T1: 5%, and T2: 10%). The results obtained showed a significant (p < 0.05) increment in growth, biochemical, and proximate parameters of T. alexandrinum with an increasing SS mixing rate. The highest productivity of T. alexandrinum fodder (1.92 kg m -2 fw) was observed in the T2 treatment as compared to the control treatment. The heavy metal analysis of shoot and root parts of T. alexandrinum showed that the contents (mg kg -1 ) of eight elements (Cd 0.02-0.13, Co 0.04-0.08, Cu 5.94-0.05, Cr 0.43-1.68, Fe 7.08-15.93, Ni 0.89-2.90, Mn 1.62-5.38, and Zn 3.30-7.04) increased significantly (p < 0.05) with SS mixing rate. The bioaccumulation factor (BAF) was below 1 except for Cu and Zn exhibiting their rapid uptake by plants from SS-treated soils. However, dietary intake modeling (DIM < 1) and health risk index (HRI < 1) studies showed that the levels of heavy metals did not exceed the permissible limits in any SS treatment. Overall, SS amendment has a positive impact on the growth, biochemical, proximate, and heavy metal characteristics of T. alexandrinum . Therefore, this study suggested a strategy for low-cost soil fertilization and fodder crop production which could sustainably benefit waste recycling.