Microneedle‐Based Biofertilizer Delivery Improves Plant Growth Through Microbiome Engineering

Abstract This study presents a microneedle‐based system for the delivery of rhizospheric biofertilizers into plant tissues to enhance growth. The microneedle structures are customizable to match leaf and stem dimensions to minimize tissue perturbation at delivery sites. The dissolving microneedles loading plant growth‐promoting rhizobacteria (PGPR) or fungi ensures rapid biofertilizer release within one minute, while the integration of an applicator facilitates user‐friendly injections. It is demonstrated that microneedle‐mediated delivery of biofertilizers into plant leaves and stems enhances Choy Sum and Kale growth more efficiently while requiring over 15% less biofertilizer quantity than traditional root inoculation. Microneedle‐mediated delivery of PGPR induces broad metabolic reprogramming, influencing energy production, biosynthesis, and amino acid metabolism. This effect is attributed to PGPR migration within the leaf and subsequent translocation to the roots, leading to shifts in root microbial composition at both the phylum and genus levels. Similarly, microneedles deliver beneficial fungi also promote Choy Sum growth by upregulating of key phytohormones, particularly abscisic acid and indole‐3‐acetic acid. Overall, “microneedle biofertilizers” offer a novel above‐ground delivery method, enabling direct biofertilizer application to plant tissues for yield improvement. This approach holds significant potential for maximizing biofertilizer efficacy, minimizing off‐target environmental impact, and enabling precision and sustainable agriculture.