Mike Ellis, manager: Research Coordination and NAMPO-Tech, Grain SA
Debbie Matteucci, chairperson, SABO
As the biostimulant market grows at a rapid rate, it is becoming increasingly more important for producers to make informed decisions regarding the available input and technologies and their applicability to maintain productive farming operations. Grain SA in collaboration with the South African Bioproducts Organisation (SABO) hosted the ‘Rethinking Crop Stimulants: New approaches for better performance’ workshop at NAMPO Park to move the conversation on biological inputs from theory into practical farm decision making.
The event brought together producers, researchers, input suppliers, extension officers, and technical advisers to discuss how innovation and biological solutions can support more resilient grain production systems. A central objective was to translate knowledge into action: to understand what crop stimulants can and cannot do, how they fit into existing soil fertility and pest-management programmes, and what practical steps producers can take before scaling biological products on farm.
Against a backdrop of variable rainfall, pressure on margins, rising input costs, and the need to maintain productive soils, the workshop focused on responsible innovation rather than product hype or marketing tricks. The main message was that biological solutions are most valuable when they are matched to a clearly identified constraint, supported by credible evidence, and integrated into sound agronomic practice.
Biostimulants, beyond the hype
Biofertilisers and biostimulants are often discussed as if they are interchangeable or as if they can substitute synthetic fertilisers, but they serve vastly different functions. Biofertilisers generally contain living organisms or biological materials that provide and/or improve nutrient availability, uptake, or use. Biostimulants are a separate category: they are substances, microorganisms, or mixtures applied to seed, plants, soil, or the rhizosphere to stimulate natural plant processes independently of their nutrient content. In practical terms, biofertilisers supply or unlock nutrients directly, while biostimulants help the plant or root zone use available resources more efficiently, support root development, improve tolerance to abiotic stress, and contribute to crop quality or yield stability.
Biostimulants have gained increasing attention as producers seek tools that support crop performance under both favourable and adverse growing conditions. As on-farm production inputs, biostimulants contribute to root development, nutrient uptake, nutrient-use efficiency, regulation of water loss through transpiration, tolerance to environmental stress, crop quality attributes, and rhizosphere health. Collectively, these effects can help plants maintain growth and productivity under stress conditions and improve recovery following adverse events. Biostimulants may also support physio-
logical processes such as photosynthesis, nutrient assimilation, and crop quality development, thereby contributing to yield stability and overall crop performance.
Unlike conventional crop protection products, biostimulants do not act directly against weeds, diseases, or insect pests, nor do they replace fertilisers, improved cultivar genetics, or sound agronomic practices. Rather, they complement well-managed production systems by enhancing plant performance with certain microorganisms, providing both biostimulatory and biocontrol benefits through their interactions within the broader ecosystem.
Another principle emphasised during the workshop was the importance of application timing. Biostimulants are generally most effective when used proactively to support plant resilience before stress occurs, rather than as remedial interventions after crop damage has already taken place. Application methods such as seed treatments are best suited for supporting early establishment and seedling vigour; in-furrow applications improve root development and soil biological activity; and foliar applications provide rapid support during periods of environmental stress, also facilitating recovery.
Above all, the adoption of biostimulants should be guided by empirical data and practical evidence rather than marketing claims. Before incorporating new products into farming systems, producers should consider evidence from replicated row-crop field trial results, consistent performance across production seasons and environments, compatibility with existing production systems, and access to reliable technical agronomic support.
A phased approach is recommended, beginning with testing on small areas before full farm-scale implementation. Furthermore, on-farm trials are critical for evaluating product performance under local soil, climate, and management conditions, and for determining how effectively biostimulants can be integrated into existing farming systems. This evidence-based approach helps ensure that adoption decisions are grounded in measurable agronomic and economic benefits.
Integrating biostimulants with sustainable agriculture
Sustainable agriculture can be viewed as a systems-based approach to sustainable crop production that links productivity, profitability, and environmental stewardship. Sustainable production systems can include principles such as minimum mechanical soil disturbance, permanent organic soil cover, and species diversification through rotations, microbe associations, and cover crops. In South African rain-fed grain systems, these principles are especially important because variable rainfall, high erosion risk, declining soil organic matter, and rising input costs all place pressure on long-term productivity.
Soil health is the capacity of soil to function biologically, chemically, and physically. Healthy soil supports crop growth, stores and cycles nutrients, regulates water infiltration and retention, buffers climate variability, and maintains a diverse soil food web. Sustainable agriculture strengthens these functions by protecting the living soil system rather than treating soil only as a medium for anchoring plants.
Crop diversification through rotations, legume intercropping, relay cropping, and cover-crop mixtures rebuilds soil function by increasing temporal and spatial diversity above and below ground. Different crop families develop different rooting patterns, residue qualities, and root exudates, which support a wider range of microorganisms and soil fauna. Crop diversification can also interrupt pest, weed, and disease cycles, improve nitrogen inputs through legumes, and stabilise production under variable rainfall. Plants are active partners in soil health because they release root exudates that feed and recruit microorganisms. These biological interactions support nutrient acquisition, stress tolerance, disease suppression, and aggregate formation. Maintaining living roots for as much of the year as possible therefore keeps the soil food web active and improves the biological capacity of the system.
Nematode community profiling links soil health with integrated pest management because both plant-parasitic nematodes and beneficial nematodes can be present in soil. Bacterivores and fungivores support decomposition and nutrient release; preda-
tors and omnivores stabilise food webs; entomopathogenic nematodes contribute to biological control; and plant-parasitic nematodes reduce crop productivity. Nematodes can also be used as bioindicators of soil food-web structure, disturbance, enrichment, and ecosystem maturity because of their functional diversity and participation in multiple food webs.
Important grain-crop pests include root-knot, lesion, pod and testa nematodes. Root-knot nematodes have high epidemic potential because they have a wide host range, can complete a life cycle in about 21 days at 26 °C, produce around a 1 000 or more eggs per female, and develop multiple generations per season. They cause root systems to malfunction through galling which impacts plant growth and yield. Lesion nematodes can also reproduce quickly, causing root lesions, impaired water and nutrient uptake, stunting, and yield loss. Nematode damage may further increase vulnerability to disease by creating pathogen entry points and by weakening natural plant defence systems.
Improving soil biodiversity and soil health reduces the impact of plant-parasitic nematodes by returning a natural balance within the soils. Various microorganisms which naturally occur or can be added as inputs either act as a barrier to nematode infestation or establish competitive food webs that eliminate favourable conditions for infestation. Regular monitoring of nematode populations is therefore an important component of integrated pest management and can support informed decisions to maintain soil health and protect crop productivity.
From workshop to field: practical takeaways
The workshop’s strongest message was to integrate, not replace. Biostimulants enhance sound fertility, soil health, and pest management programmes; they should not be treated as a silver bullet or as a substitute for fertilisers, pesticides, good genetics, or disciplined agronomy. Producers benefit when using these products as tools to improve root establishment, stress resilience, nutrient uptake, potential yield gains, and long-term soil health benefits linked to microbes, organic matter, and rhizosphere function.
Product choice should start with the farm constraint or goal. When deciding which input to select, producers should assess whether the product is registered under Act 36 of 1947 and has a clear mode of action, a credible label, defined active ingredients or strain identity, quality-control standards, application guidance, compatibility informa-
tion, and independent field evidence. A product that performs well in one crop, soil type, or season may not deliver the same outcome under different local conditions and crop varieties. Using products that are not registered for the intended use leaves a producer exposed should they need to claim from insurance or manufacturers for crop failure.
Testing before scaling up is critical. Small, well-planned on-farm trials allow for compa-
risons between treated and untreated soils under the same management, cropping regime, pest pressure, weather and soil conditions. Soil sampling and testing should form part of this process so that biological products are evaluated against a clear understanding of fertility status, organic matter, pH, compaction, nematode pressure, and other limiting factors.
Recordkeeping turns experience into evidence. Producers should record the product name, batch number, rate, timing, application method, weather conditions, tank-mix partners, crop stage, field history, and measured results. Over time, these records help build a farm-specific evidence base and support better decisions about whether, where, and how biological products fit into the production system. While this seems to be an unnecessary burden and often necessitates more human capital, this is a sure way to future-proof farming practices and enable producers to remain agile under challenging conditions.
Conclusion
The workshop highlighted that biological solutions, including biostimulants, should not be viewed as standalone inputs or quick fixes, but as tools that can complement sound agronomic practices when matched to a clearly identified constraint and supported by credible evidence. This is no longer a portion of the industry reserved for the few expe-
rimenters; this is necessary technology for all producers to adopt in relevant spheres to foster resilience in agricultural systems.
As the biostimulant market continues to grow, informed decision making will become increasingly important for producers seeking to determine which products are appro-
priate for their farming operations. By understanding what these products can and cannot do, and integrating them appropriately into soil fertility, crop and pest-manage-
ment programmes, producers can make more responsible and effective use of biological inputs.
Together with practices that build and maintain soil health, these approaches contri-
bute to a functional soil ecosystem capable of supporting improved crop growth and development. Healthy soils provide the foundation for diverse and productive farming systems by improving nutrient availability, supporting beneficial biological activity, and creating stable growing conditions. Ultimately, responsible innovation and the effective integration of biological solutions can contribute to greater productivity, long-term sustainability, and more resilient agricultural systems.
