By-products of insect farming as a novel sustainable biofertilizer for crops.

The development of sustainable high-yield farming practices is crucial to support a growing human population while providing long-term solutions for the environmental impact of intensified agriculture. Nutrient-rich bio-residuals generated through the industrial production of insects hold a high but underexplored potential as an alternative to less sustainable fertilizers. In a two-year field experiment, we show that mustard plants grown in insect-exuviae-amended soil perform as well or even better than plants grown in soil amended with reference organic fertilizers. Improved plant performance was driven by increased plant growth in terms of height and width, a larger number of flowers produced, more interactions with pollinators, and a larger seed production compared to untreated plants. A parallel greenhouse experiment revealed that native root-associated microbial communities in exuviae-amended soil were more species-rich, less variable, and were characterized by several well-known plant-growth-promoting rhizobacteria compared to those found in unamended soil or soil treated with reference fertilizer. Collectively, these findings demonstrate that valorizing insect-based bio-residuals can improve agricultural sustainability while simultaneously supporting a circular economy.