Vol. 10, Issue 6, Part A (2024)

Abstract
In order to improve the fertility of a sandy soil contaminated with polycyclic aromatic hydrocarbons, increasing quantities of biosolids obtained from the treatment and drying of septic tank sludge (control or (T₀), soil not contaminated with hydrocarbons; (T₁), soil contaminated with hydrocarbons; (T₂), hydrocarbon-contaminated soil to which we added 15% biosolids; (T₃), contaminated soil to which we added 30% biosolids and (T₄), contaminated soil to which we added 45% biosolids) was mixed with contaminated soil to test the germination and growth of roots and stems of Abelmoschus esculentus and Amarantus cruentus after 90 days. Results showed that on day 5 following soil application of biosolids, the germination rate of Abelmoschus esculentus was ≥ 80% in all substrates, while Amarantus cruentus seeds germinated at over 80% only in treatments T₃ and T₄. Root growth on day 14 showed that the length of okra (Abelmoschus esculentus) roots was significant for T₄ substrates first and then T₃. Stem length was marked for T₄ and T₃. Abelmoschus esculentus roots and stems developed well in T₄ and T₃ substrates. The physicochemical properties of the substrates indicated that total nitrogen, total phosphorus, assimilable phosphorus, total organic carbon and electrical conductivity increased in substrates containing biosolids. Doses of 30 and 45% biosolids applied to hydrocarbon-contaminated soil had a positive effect on the germination and growth of roots and stems of two, reflecting the reduced toxicity of hydrocarbon-contaminated soil due to biosolids.