Comparison of black soldier fly Hermetia illucens (Diptera: Stratiomyidae) frass to chemical and organic fertilizers on arthropod abundance and edamame plant performance

Abstract The use of Hermetia illucens L. (Diptera: Stratiomyidae) larvae for the bioconversion of organic waste into protein and frass is gaining popularity. Although frass of H . illucens has been proposed as an organic fertilizer, its relative impact on crop productivity and soil organism diversity remains insufficiently understood compared to other fertilizers. We, therefore, evaluated the effectiveness of frass of H . illucens relative to commercial chemical (NPK) fertilizer and compost in edamame ( Glycine max (L.) Merr.) production while also considering their potential within the circular economy framework. Edamame plants in NPK plots averaged 71.1 ± 0.79 cm in height, which was not significantly different from frass of H . illucens plots at 69.47 ± 3.22 cm ( p > 0.05). The frass of H . illucens plots also had the highest average yield (84.27 ± 8.79 g/plant), which did not differ significantly from NPK plots (85.05 ± 7.37 g/plant) ( p > 0.05). In addition, the application of frass of H . illucens increased the abundance of soil arthropods (5.62 ± 0.99 individuals/plot), exceeding all other treatments ( p < 0.05). Predators were especially abundant in frass of H . illucens plots (3.87 ± 0.91 individuals/plot) compared to other treatments ( p < 0.05). Ground beetles (Coleoptera) were the dominant arthropod group across all treatments. Conversely, foliar arthropod abundance was significantly affected by fertilizer type, with frass of H . illucens demonstrating the highest increase across trophic levels ( p < 0.05). Overall, our findings indicate that frass of H . illucens not only enhances edamame plant growth and yield but also fosters greater soil and foliar arthropod abundance. By recycling organic waste into a valuable agricultural input, frass of H . illucens contributes to improved biodiversity and aligns with circular economy principles, offering a more sustainable approach to crop production.