Application of Black Soldier Fly Frass, <i>Hermetia illucens</i> (Diptera: Stratiomyidae) as Sustainable Organic Fertilizer for Lettuce, <i>Lactuca sativa</i> Production

In recent years, black soldier fly (BSF) has been shown to efficiently convert organic waste into nutrient-rich larval biomass while generating frass as the main by-product. This work aims to investigate the potential of BSF frass (BSFF) as an organic fertilizer for agricultural production. BSFF was produced by recycling household waste using BSF larvae, and a portion was taken to the lab for physicochemical and microbial analyses before the field trial on lettuce growth and health. The field trial consisted of two doses of BSFF (15 t·ha-1 and 30 t·ha-1) and one dose of urea (0.214 t·ha-1). An unfertilized plot was prepared and used as a control, and the effects on lettuce growth were assessed using agronomic parameters while the health effects were assessed using parameters such as: the number of leaves affected per plant, the incidence of affection, the severity of the affection and the microbial analysis. BSFF exhibited acceptable physicochemical properties as an organic fertilizer. Its application improved the growth parameters of lettuce plants compared to urea and control. The application rates of 15 t·ha-1 and 30 t·ha-1 did not reveal any significant difference (p > 0.05). Further studies are therefore needed to determine the minimum applicable dose. The health parameters of the lettuce plants were slightly altered regardless of the treatment and the microbial analysis of the affected leaves revealed pathogenic microorganisms. We therefore recommend that decontamination methods be considered when producing BSFF as an organic fertilizer.