Effects of Wastewater Irrigation from Kalshingi Fish Farm on the Microbial and Physicochemical Characteristics of Agricultural Soils

Abstract

Agriculture and aquaculture are vital components of global food security. However, using fish farm wastewater for irrigation raises concerns about its effects on soil health and microbial communities. This study assessed the effects of fish farm wastewater from the Kalshinge Fish Farm on soil bacterial diversity, physicochemical properties, and implications for agricultural productivity. Soil samples were collected from the impacted and control plots at the Kalshinge Fish Farm, and key soil parameters, including pH, electrical conductivity, salinity, and nutrient concentrations, were measured. Bacterial isolates were identified, and their antibiotic sensitivities were evaluated. The results showed that the pH values ranged from 4.72 to 7.00, electrical conductivity from 2470 to 2930 µS/cm, and salinity between 5.82 and 7.65 mg/100 g in the impacted soils, which were higher than those in the control soils. The total heterotrophic bacterial count in impacted samples ranged from 0.007 to 0.075 CFU/mL, with sample E showing the highest count (0.075 CFU/mL). Bacterial species, including Escherichia coli (80% occurrence), Pseudomonas aeruginosa (80%), and Klebsiella pneumoniae (60%), were prevalent in the affected soils. Antibiotic resistance was observed in isolates, particularly Escherichia coli and Klebsiella pneumoniae, which showed resistance to Amoxicillin and Azithromycin. Wastewater can enhance soil fertility but also poses risks of soil degradation and the spread of antibiotic-resistant bacteria. This study highlights the need for sustainable management to minimise the impact of irrigation. Future research should examine the long-term effects on microbial diversity and explore strategies to prevent the spread of antibiotic resistance in agricultural systems.