Evaluation of biostimulants from nature-based substances: promoting crop resilience and land sustainability models

In the context of current climate change and ecosystem degradation, agricultural sustainability has been positioned as a core strategic objective to meet food demands while preserving natural resources. The latest Intergovernmental Panel on Climate Change (IPCC) report states that the agricultural sector is responsible for about 23% of net anthropogenic greenhouse gas emissions, driven mainly by the intensive use of synthetic inputs such as fertilizers, pesticides, and non-regenerative soil management practices. Bio-based formulations represent a range of solutions derived from natural components (e.g., active ingredients from algae and plants) that stimulate healthy crop growth and protect against pests. Biostimulants are substances or organisms that enhance plants' resilience to biotic and abiotic factors. These biostimulants are essential agents in organic agriculture, as they improve the physiological pathways of plants, allow for enhanced nutrient uptake, and strengthen their resistance to the effects of extrinsic factors. Furthermore, they promote land health by stimulating beneficial microbiota and incorporating organic matter, which enables agroecosystem sustainability and eases organic certification. European fertilizer legislation and the European Biostimulants Industry Council (EBIC)'s guidelines require the marketing of a product as a biostimulant to be supported by scientific evidence demonstrating its efficacy and precise mechanism of action. This review presents an updated view of plant biostimulants, evaluating their efficacy, mechanisms of action, and impact on plants' resistance within sustainable soil management frameworks. It includes a discussion of various crops' resilience and land sustainability models, focusing mainly on empirical and conceptual approaches, while also acknowledging mathematical and simulation models as complementary tools for future research.