Sewage sludge-based organomineral fertilizer: A pathway to enhanced soil fertility and chickpea production

Purpose: Sewage sludge compounds possess physical and chemical attributes that make them well-suited for formulating fertilizers intended for agricultural purposes. Within this framework, the research aimed to assess the effects of utilizing organomineral fertilizers derived from sludge on soil fertility and chickpea yield. Method: The study was conducted in a randomized complete block design, with five replications, in a 2×2+2 factorial scheme, consisting of two organic sources for organomineral fertilizer production (composted sludge - SC or sludge biochar - SB), two fertilizer forms (granular-GRA or powder-POW), and two additional controls (mineral fertilization with NPK at a 04:15:04 ratio, and unfertilized-NF). The chickpea production and soil chemical attributes were characterized. Results: The organomineral fertilization with composted sewage sludge and sewage sludge biochar, in the forms of powder or granules, increased soil fertility, and enhanced production characteristics. Fertilization with LC and BL resulted in soil organic carbon (OC) content of 8.00 and 8.60 g/kg, while treatments with NPK and without fertilization had 6.50 and 7.30 g/kg, respectively. Grain dry matter and total dry matter varied from 4.80 to 5.70 and 17.40 to 19.10 g per plant in fertilized treatments, respectively. In the unfertilized plots, the averages were 0.30 and 3.40 g per plant. Conclusion: The use of organomineral fertilizer consisting of composted sludge or in granulated form increased straw production by 19% and 5.70 times, compared to mineral fertilization and the control (no fertilization), respectively. This indicates the potential for chickpea production similar to that obtained in treatments receiving only mineral fertilization. Research Highlights • Fertilizers from composted sludge or sludge biochar enhance soil fertility. • Organomineral fertilizers increase soil organic matter content. • Organomineral fertilizers enhance soil cation exchange capacity. • Granulation of composted sludge increases chickpea residue production. • Stabilized sludge in powder or granulated form can serve as an alternative fertilizer source. • Organomineral and mineral NPK fertilizers are equivalent in chickpea production.