Microalgal biomass as a biofertilizer for pasture cultivation: plant productivity and chemical composition

Abstract

The objective of this work was to evaluate the effect of fertilization of a marandu grass pasture with microalgae biomass produced during the treatment of a wastewater from a dairy farm as a nitrogen source. The experimental design consisted of randomized blocks with three treatments (C - without fertilization, Q - chemical fertilization, and B - biological fertilization) with seven replications. The microalgae biomass considered in biological fertilization showed 1,992 mgL−1 of phosphorus, 1,657 mgL−1 of nitrogen and pH 8.4. The accumulated dry mass productivity was highest in chemical treatment Q (15,551 kgha−1), followed by B (14,857 kgha−1). Regarding the dry matter content, B stood out, with 23%, followed by C (21%). For crude protein (CP) and ash contents, Q presented the highest values (12.81 and 8.71%, respectively), followed by B (10.27 and 7.17%, respectively for CP and mineral matter content). The lowest neutral detergent fiber content was observed in Q (62.55%), followed by B (62.85%). The biological treatment had similar plant productivity compared to the treatment with chemical conventional fertilizer. Regarding nitrogen utilization efficiency and nitrogen recovery, chemical treatment showed statistical difference compared to microalgae biomass. Using microalgae biomass as biological fertilizer proved to be an interesting alternative for pasture fertilization in the context of a green circular economy.