Microalgal biomass as a partial replacement for chemical fertilizers in barley cultivation

The overuse of nitrogen fertilizers causes nutrient losses through leaching and volatilization. Replacing them partially with organic alternatives like microalgal biomass offers a sustainable solution, improving soil properties, reducing nitrogen losses, and minimizing environmental harm. We aimed to evaluate the use of Spirulina platensis biomass as a partial replacement for chemical fertilizers in brewing barley cultivation. Trials were conducted to replace chemical fertilizer with S. platensis biomass based on nitrogen content. The applications included in-row treatments (50% and 100%) and topdressing (10%, 20%, and 40%). In addition, a seed treatment trial using microalgal biomass extract (5%, v/v) was also performed. The replacement of chemical fertilizer with microalgal biomass maintained brewing barley quality and soil nitrogen levels, highlighting its potential as a multifertilizer. Higher nitrogen accumulation was observed in barley grains in the treatments with in-line replacement and the lowest level of topdressing replacement (p<0.05). Greater accumulation of phosphorus, potassium, calcium, and magnesium was observed in barley grain in the trials that performed the replacement of conventional fertilizers in topdressing (up to 0.28%). There was no difference in productivity between treatments, indicating that crop yield was not affected by the replacement of fertilizers. There was an increase of 10% in the percentage of first-quality grains in the replacement trials when compared to the seed treatment trial. Thus, partial replacement of chemical fertilizers with microalgal biomass in barley fields enhances sustainability while maintaining productivity. Using agro-industrial residues for biomass production reduces environmental impact and supports economic and ecological goals.