Biostimulants
Biostimulants are a diverse group of substances, microorganisms, and formulations applied to plants or soils with the primary purpose of enhancing plant growth, yield, quality, and resilience to stress, without being classified as fertilisers or pesticides. They represent a rapidly expanding area in modern agriculture, offering sustainable alternatives to chemical inputs while supporting soil health and crop productivity.
Definition and Concept
Unlike fertilisers, which provide nutrients, or pesticides, which protect against pests and diseases, biostimulants work by stimulating the plant’s natural processes. They improve nutrient uptake, increase tolerance to abiotic stresses such as drought, salinity, and temperature extremes, and enhance crop quality parameters. The European Biostimulants Industry Council (EBIC) defines them as products that stimulate natural processes to benefit nutrient use efficiency, abiotic stress tolerance, and crop quality, regardless of nutrient content.
Types of Biostimulants
Biostimulants encompass a wide range of naturally derived and synthetic products. The main categories include:
- Humic and fulvic acids: Organic molecules derived from soil or decomposed plant matter that enhance nutrient uptake and root growth.
- Seaweed and algal extracts: Rich in phytohormones, polysaccharides, and minerals that stimulate growth and improve stress tolerance.
- Protein hydrolysates and amino acids: Improve nitrogen assimilation, enzyme activity, and stress resistance.
- Microbial biostimulants: Beneficial microorganisms such as rhizobacteria, mycorrhizal fungi, and Trichoderma species that promote nutrient uptake and soil health.
- Chitosan and other biopolymers: Derived from natural sources, these enhance plant defence responses and growth.
- Inorganic compounds and signalling molecules: Substances like silicon, phosphites, and plant hormones that influence physiological activity.
Mechanisms of Action
Biostimulants exert their effects through multiple pathways:
- Enhancing root development, increasing the surface area for nutrient and water absorption.
- Improving nutrient use efficiency, reducing dependency on chemical fertilisers.
- Inducing systemic resistance against abiotic stresses such as drought, frost, and salinity.
- Stimulating microbial activity in soil, improving soil fertility and structure.
- Promoting photosynthesis and metabolic activity, thereby improving yield and crop quality.
Applications in Agriculture
The use of biostimulants has become increasingly important in sustainable agriculture, especially under the constraints of climate change and environmental concerns. Applications include:
- Field crops such as cereals, pulses, and oilseeds for enhanced yield and resilience.
- Horticultural crops such as fruits, vegetables, and ornamentals to improve quality, colour, and shelf life.
- Soil remediation by restoring microbial balance and organic matter content.
- Water-stressed regions, where biostimulants reduce drought impact.
Advantages of Biostimulants
- Sustainability: Reduce reliance on synthetic fertilisers and pesticides.
- Stress tolerance: Improve crop survival under adverse climatic conditions.
- Soil health: Foster beneficial microbes and improve soil structure.
- Quality enhancement: Increase nutritional value, flavour, and post-harvest life of produce.
- Eco-friendly: Derived mostly from natural resources, they have low environmental impact.
Limitations and Challenges
Despite their benefits, biostimulants face several challenges:
- Lack of standardisation: Variability in formulations and performance under different conditions.
- Regulatory gaps: Classification and approval processes vary between countries.
- Limited awareness among farmers, particularly smallholders.
- Cost factor, as many formulations are relatively expensive compared to conventional inputs.
- Need for scientific validation to support efficacy claims and farmer confidence.
Global and Indian Scenario
Globally, the biostimulant market is expanding rapidly, with Europe and North America leading in adoption. The European Union has included biostimulants within its regulatory framework under the Fertilising Products Regulation (2019).
In India, the adoption of biostimulants is growing, particularly in horticulture and organic farming. The Ministry of Agriculture has introduced guidelines for regulation under the Fertiliser Control Order (FCO). Given India’s challenges of declining soil fertility, high fertiliser usage, and climate stress, biostimulants are being seen as a crucial tool for sustainable agricultural intensification.
Future Prospects
Biostimulants are expected to play a vital role in addressing the dual challenge of increasing agricultural productivity and maintaining environmental sustainability. With advances in biotechnology, precision agriculture, and integrated nutrient management, their application is likely to expand further. Strengthening research, regulation, and farmer awareness will be key to realising their full potential in the agricultural sector.
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