Biostimulants in Low-Input Agroecosystems: Mechanisms, Crop Responses and Future Prospects for Sustainable Agriculture in South Africa

This review aims to synthesise existing knowledge on the efficacy, underlying mechanisms, and practical relevance of biostimulants within low-input agroecosystems, with particular emphasis on South Africa as a representative semi-arid, resource-constrained agricultural system, while highlighting broader implications for similar low-input agroecosystems in sub-Saharan Africa. This review paper reviews peer-reviewed and selected grey literature sources published between 1997 and 2026, retrieved through structured searches of Scopus, Web of Science, and Google Scholar using predefined keywords related to biostimulants, sustainable agriculture and South Africa. Across the literature, there is general agreement that biostimulants may indirectly support biodiversity through improved soil biological activity and reduced dependence on synthetic inputs, although direct field evidence remains limited. Methodologically, most studies are conducted under controlled or semi-controlled conditions, including greenhouses, growth chambers, and pot experiments. While these approaches allow for mechanistic understanding and precise variable control, they often fail to capture the complexity of field environments typical of low-input farming systems. This review synthesises peer-reviewed literature identified through structured searches of major databases utilising terms related to biostimulants, with an emphasis on studies conducted in both controlled environments and field settings. Evidence suggests that biostimulants can enhance plant physiological performance, improve stress tolerance, and contribute to more efficient resource use when integrated into appropriate management practices. However, their effectiveness is highly context-dependent, and they should not be considered substitutes for soil fertility management or sound agronomic practices. Future research, particularly in South Africa as a representative semi-arid and resource-constrained system, should prioritise field-based assessments and incorporate ecological indicators such as species abundance, pollinator visitation, and ecosystem resilience under biostimulant regimes to generate more robust and context-relevant evidence.