Planned Application of Sewage Sludge Recirculates Nutrients to Agricultural Soil and Improves Growth of Okra (Abelmoschus esculentus (L.) Moench) Plants

Ebrahem M Eid,Mohamed T Ahmed,Sulaiman A Alrumman,Mohamed Hashem,Yasser S Mostafa,Afaf A Nessem,Nasser Sewelam,Mostafa A Taher,Saad A M Alamri,Ahmed F El-Bebany,Tarek M Galal,Kamal H Shaltout

doi:10.3390/su14020740

Abstract

The aim of this study was to investigate the feasibility of using sewage sludge (SS) biosolids as a low-cost soil fertilizer to improve soil characteristics and crop yields. Okra (Abelmoschus esculentus (L.) Moench) plants were grown in soil supplemented with different concentrations of SS (0, 10, 20, 30, 40, and 50 g/kg). The results showed that SS soil application led to improved soil quality with a 93% increase of organic matter (at SS dose of 10 g/kg), decreased pH (a reduction from 8.38 to 7.34), and enhanced macro- and micro- nutrient contents. The levels of all the investigated heavy metals (HMs; Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in the postharvest SS-amended soil were within the prescribed safe limits. The application of SS to soil considerably enhanced the growth parameters of okra plants. Total biomass increased 13-fold and absolute growth rate increased 10-fold compared to plants grown in nonamended (control) soils. Among the applied SS doses, the 10 g/kg SS dose led to the highest values of the measured growth parameters, compared to those of plants grown in control soils. The induced growth at 10 g/kg SS was accompanied by a substantial increase in metal content in roots, stems, leaves, and fruits; however, all levels remained within safe limits. Consequently, the data presented in this study suggest that SS could be used as a sustainable organic fertilizer, also serving as an ecofriendly method of SS recycling.

Highlights

The results of this study showed that the application of sewage sludge (SS) to soil led to improved soil quality with higher and enhanced the growth and yield parameters of okra plants
Chemical Properties of the Sewage Sludge and Precultivation Soil Used in the Pot Experiment
The results indicated that SS contained relatively high levels of toxic heavy metals (HMs), such as Pb, but these were within the permissible limits for SS (Table 1)

Summary

Introduction

Among the numerous types of solid waste, sewage sludge (SS) is an important type of organic waste. Due to population expansion, dwindling natural resources, and the cur-rent energy crisis, the relevance of establishing a sustainable strategy for eco-friendly solid waste management cannot be overstated. The inappropriate disposal of SS and other biowastes poses a major threat to environmental quality, resulting in issues such as groundwater pollution and soil deterioration [1]. The use of SS as a soil fertilizer is gaining popularity. SS can be utilized to improve the physical and chemical properties of soil, such as pH, fertility, porosity, bulk density, Sustainability 2022, 14, 740.

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