Impact of trace metals in fish waste-based organic fertilizer on growth promotion and nutritional components of spinach plant (Spinacia oleracea L.)

Fermented fish waste is increasingly utilized as a nutrient-rich organic fertilizer to enhance soil fertility and sustainable crop production. However, limited data exist on how trace metals in fish waste–based fertilizers affect plant growth and food safety. Therefore, our current study addresses this gap by evaluating the effects of liquid organic fertilizers (LOFs) derived from fermented carp fish waste on the growth and nutrient composition of spinach (Spinacia oleracea L.). This experimental study investigated varying LOF concentrations (10–50 ml) compared to water, NPK, and control treatments over a 60-day growth period. The overall results demonstrated that LOF applications, particularly at 40 and 50 ml, significantly improved leaf growth, photosynthetic pigments, and essential mineral accumulation while maintaining trace metal levels within safe consumption limits. These findings suggest fish waste–based LOFs can effectively promote spinach growth and nutritional quality, offering an eco-friendly and sustainable alternative to chemical fertilizers that supports soil health and reduces environmental impact. Furthermore, our study provides a novel and comprehensive evaluation of the agronomic benefits and potential health risks associated with trace metals in fish waste-derived fertilizers. This aspect has rarely been explored in previous research.