Biostimulants in Agriculture II: Towards a Sustainable Future

Book excerpt: Modern agriculture needs to review and broaden its practices and business models, by integrating opportunities coming from different adjacent sectors and value chains, including the bio-based industry, in a fully circular economy strategy. Searching for new tools and technologies to increase crop productivity under optimal and sub-optimal conditions and to improve resources use efficiency is crucial to ensure food security while preserving soil quality, microbial biodiversity, and providing business opportunities for farmers. Biostimulants based on microorganisms or organic substances obtained from renewable materials represent a sustainable, efficient technology or complement to synthetic counterparts, to improve nutrient use efficiency and secure crop yield stability. Under the new European Union Regulation 2019/1009, plant biostimulants were defined based on four agricultural functional claims as follows: Plant biostimulants are products that stimulate plant nutrition processes independently of the product's nutrient content with the sole aim of improving one or more of the following characteristics of the plant and/or the plant rhizosphere: 1) nutrient use efficiency, 2) tolerance resistance to (a)biotic stress, 3) quality characteristics or 4) availability of confined nutrients in the soil or rhizosphere’. Many diverse natural substances and chemical derivatives of natural or synthetic compounds, as well as beneficial microorganisms, are cataloged as plant biostimulants including i) humic substances, ii) plant or animal-based protein hydrolysates, iii) macro and micro-algal extracts, iv) silicon, v) arbuscular mycorrhizal fungi (AMF) and vi) plant growth-promoting rhizobacteria (PGPR) belonging to the Azotobacter, Azospirillum and Rhizobium genera.