Formulation challenges associated with microbial biofertilizers in sustainable agriculture and paths forward

Sustainable increase in agriculture productivity is confronted by over-reliance and over-use of synthetic chemical fertilizers. With a market projection of $5.02 billion by 2030, biofertilizers are gaining momentum as a supplement and, in some cases, as an alternative to chemical fertilizers. Biofertilizers can improve the nutritional supply to the plant and simultaneously can improve soil health, reduce greenhouse emissions, and hence directly contribute towards environmental sustainability. Plant growth-promoting microbes (PGPMs) are particularly receiving significant attention as biofertilizers. They are widely known for their ability to improve plant growth via increasing nutrient availability and use efficiency. However, except for a few successful cases, the commercialization of PGPM-based inoculants is still limited, mainly due to lack of field efficacy and consistency. Lack of effective formulation technologies that keep microbial inoculants viable during storage, transport and field application is considered one of the key factors that drive inconsistent efficacy of microbial biofertilizers. In this review, we identify current challenges associated with the application and formulation of microbial inoculants. We propose future paths, including advancement in formulation technologies that are potentially efficient, eco-friendly and cost-effective. We argue that to enhance the global adoption of biofertilizers, new innovations based on transdisciplinary approaches are indispensable. The emerging framework should encompass a robust quality control system at all stages. Additionally, the active partnership between the academic and industry stakeholders will pave the way for enhanced global adoption of microbial fertilizers.