Harnessing the Power of Biostimulants: A Comprehensive Review of Their Role in Enhancing Agricultural Productivity and Sustainability

Biostimulants are becoming essential and complementary tools in modern agriculture, offering an innovative and environmentally friendly approach to enhance crop production and resilience. This review explores biostimulant classification—including humic substances, seaweed extracts, protein hydrolysates, and beneficial microorganisms—and elucidates the complex mechanisms of action through which they modulate plant physiology and biochemical and molecular processes. A major focus is placed on their demonstrated ability to significantly enhance nutrient use efficiency, stimulate root growth, improve water retention, and activate plant defense systems, thereby increasing tolerance to a wide plethora of stressors like drought, salinity, and extreme temperatures. Despite their proven efficacy, the broader adoption of biostimulants faces significant hurdles, including inconsistent product formulation, fragmented regulatory frameworks, and a limited understanding of their long-term effects under diverse field conditions. By emphasizing recent scientific and technological innovations, this review proposes a framework for research and practical application. Finally, biostimulants are part of the new technologies capable of improving plant resistance to abiotic stress and adapting agricultural systems to climate change, thanks to improved productivity and efficiency in the use of production inputs and natural resources. Advances in understanding the mechanisms of action of biostimulants will enable us to modulate the concept of plant nutrition and improve crop management.