Co-Author of the article: Dr Ida Wilson
In recent years, biostimulants have become an important tool for farmers to manage the productivity of their crops. Biostimulants are known to have various benefits for crop production. One product may induce one or more of the following effects. It could increase plant growth, pest and disease resistance, nutrient uptake efficiency, crop productivity, and quality of fresh produce. These benefits are not necessarily gained from a specific kind of biostimulant, and various products will have been proven to benefit plants in some of the ways mentioned. A secondary benefit of the use of biostimulants is improvement in soil health (as root growth is stimulated as is interaction with beneficial soil microbial organisms). Using biostimulants also supports the long-term sustainability of crop production and the preservation of natural resources. Interest in plant biostimulants has surged over the past decade, fuelled by researchers' and farmers' growing demand for eco-friendly solutions to boost crop performance.
As the human population grows, sustainable crop production has become critical to secure food, feed, and fiber as needed in the future. Sustainable agriculture promotes efforts that safeguard ecosystems and biodiversity while emphasizing the judicious use of resources like soil, water, and energy sources. Producing fresh produce and all plant-based products (as well as animal-based products) while preserving the environment, fostering economic viability, and raising the standard of living for farming communities is the ultimate objective of sustainable agriculture. More detailed information on biostimulants and how they may support a sustainable future for crop farming is discussed in the following section.
What are biostimulants?
Biostimulant products are substances or microorganisms derived from natural resources used on plants or soils to enhance overall plant and soil health and productivity. They work by stimulating the plants' natural processes or enriching the soil microbiome, which results in a myriad of secondary benefits in the production system. As stated earlier, each unique product will have a different mode of action and specific outcomes on crop productivity.
Why are biostimulants needed?
Global climate instability is creating challenges for crop production, with unpredictable weather patterns, erratic precipitation, and frequent droughts and floods impacting many agricultural regions. Plants now face more frequent abiotic stresses (e.g., heat, salinity, wind, hail) and biotic pressures from pests and pathogens, which thrive in warmer temperatures and may resist conventional pesticides for many reasons, including pesticide resistance or lowered efficacy at higher temperatures. The growing population and limited natural resources urge advances in crop productivity. However, soil degradation, pollution, and limited land for expansion intensify the pressure on crop production and crop production practices. Agrochemicals, while useful, can harm beneficial organisms, be toxic to the environment, and be harmful to human health, highlighting the urgent need for alternative methods to enhance crop productivity and protect plant health.
What are the types of biostimulants?
Biostimulants are produced from various sources, including the following list.
- Flavonoids: These polyphenolic compounds aid stress tolerance, pest resistance, and microbe colonization (Shah and Smith 2020).
- Humic & Fulvic Acids: Organic compounds that enhance soil structure, nutrient availability, and microbial activity, leading to better plant growth and soil health (Godlewska et al. 2021). Found in soil, these acids enhance nutrient absorption, root growth, and drought tolerance.
- Beneficial Microbes: Mycorrhizal fungi and bacteria that promote growth, quality, and resistance to salt and other stresses (Alori and Babalola, 2018).
- Chitosan: A chitin derivative that improves drought tolerance and strengthens plant defenses (Povero et al. 2016)
- Seaweed Extracts: Rich in polysaccharides and antioxidants, these extracts improve crop yield, stress resistance, and nutrient uptake (Khan et al. 2009)
- Plant Extracts: These extracts enhance chlorophyll production and support photosynthesis. Carrilo et al. 2019)
The effects of biostimulants on plants
Biostimulants may encourage root development, chelate nutrients to increase their availability and cultivate symbiotic connections like those between legumes and Rhizobium bacteria, enhancing nutrient uptake (Halpern et al. 2015). Furthermore, biostimulants improve photosynthetic efficiency, growth processes, metabolic pathway regulation, hormonal balance, and metabolic balance in plants (Baltazar et al., 2021). They also play a critical role in raising stress tolerance by enhancing stress resistance, boosting antioxidant defenses, optimizing water usage efficiency, and fortifying cellular structures.
Biostimulants and environmental preservation
Biostimulants may play a key role in the preservation of the environment in sustainable agriculture. The effects biostimulants have on plants align with the fundamental tenets of sustainable agriculture. These are the preservation of ecological balance (by being environmentally friendly), reduction of the use of products that have negative effects on the environment, and conserving natural resources. By enhancing plant health and stress resilience, biostimulants decrease the demand for synthetic chemicals and promote the use of 'softer' pest management practices that can be used in organic agriculture, such as integrated pest management (IPM). Reducing pesticide use may lead to less pesticide runoff entering water bodies, thereby preserving aquatic habitats. Integrated pest management, which lowers the reliance on pesticides, is also favorable to pollinators and beneficial insects.
Biostimulants and economic viability
Through improving resource efficiency and lowering input costs, biostimulants may contribute to the economic viability of sustainable agriculture, supporting the resilience and long-term profitability of farming operations. Biostimulants may lessen the need for synthetic fertilizers, insecticides, and herbicides by enhancing plant health and growth. Farmers can reduce their input costs and increase their profit margins by depending more on natural alternatives – but only with scientific proof backing their efficacy.
Biostimulants and social health
Biostimulants play a crucial role in enhancing social well-being within sustainable farming by fostering the production of safe, nutritious food. Particularly in rural communities, where crop productivity is low, supplying these farmers with biostimulants (through a governmental grant or aid scheme) could revitalize rural communities. The potential of biostimulants to improve plant health and growth may reduce the need for repeated and overuse of synthetic pesticides, given that it is adopted as a wide-scale practice. Lower pesticide use will lower the incidence of residues on fresh produce and may support better public health. On-farm health for farm workers and those who live near farms where pesticides are used will also benefit. Some research has also proven that fresh produce grown with biostimulant products as input was more nutritious than those where pesticides were applied repeatedly (over-use). Biostimulants, therefore, hold the potential to help secure nutritious food, which has become a crisis worldwide, where millions are undernourished (ref). Additionally, biostimulants contribute to job creation by boosting farm productivity, which in turn strengthens local economies.
Biostimulants and climate resilience
Biostimulants improve various adaptive and mitigation strategies, increasing climate resilience in sustainable agriculture. By enhancing soil organic matter and plant health, they promote soil carbon sequestration by raising the soil's ability to absorb carbon dioxide from the atmosphere. This is consistent with techniques like cover crops and conservation tillage, which are proven to improve soil carbon storage. Furthermore, by optimizing photosynthesis and maximizing nutrient intake, biostimulants may lower the demand for synthetic fertilizers, which are linked to significant nitrous oxide emissions. In the future, as biostimulants are more widely adopted, they may significantly contribute to reducing greenhouse gas emissions.
Additionally, they increase plant resistance to drought and lower the demand for irrigation, which increases water-use efficiency and helps conserve water during dry spells. The ability of biostimulants to protect plants against drought stress may also ensure harvests in instances where the drought would destroy the entire crop. Biostimulants also enhance biodiversity and ecosystem services, which are essential for adjusting to changing climatic circumstances, by promoting plant health and resilience, as well as the resilience of all living creatures in the plant production system. They increase farms' overall resilience and productivity by making crops more resilient to pests and adverse weather. Biostimulants are essential for reducing the effects of climate change and improving the resilience of agricultural systems because of these mechanisms.
Biostimulants and environmental preservation
Biostimulants play a vital role in preserving natural resources by enhancing soil health, promoting efficient nutrient use, and reducing environmental impact. By improving soil structure and increasing organic matter content, biostimulants help prevent soil erosion and degradation, leading to better water retention and quality. This not only supports plant growth but also safeguards water resources by minimizing runoff and nutrient leaching, which can lead to water pollution. Furthermore, biostimulants enhance nutrient uptake efficiency, allowing plants to thrive with lower inputs of synthetic fertilizers. This reduction in chemical use helps preserve surrounding ecosystems by decreasing the risk of chemical runoff that can harm aquatic life and contaminate water supplies (Zhang et al. 2017).
Biostimulants and soil health
Biostimulants are increasingly recognized for their positive impact on soil health by stimulating biological processes in plants that support the surrounding soil ecosystem. Certain biostimulant components encourage root growth and improve root structure, allowing plants to access nutrients more effectively across a larger soil volume. Healthier roots, in turn, enhance overall soil structure, aiding water infiltration and retention. Compounds such as humic and fulvic acids found in many biostimulants further improve soil health by forming stable soil aggregates, which retain moisture and reduce erosion. Biostimulants play a crucial role in fostering a balanced soil microbiome. By promoting beneficial microorganisms, they enhance nutrient cycling and help suppress soil-borne diseases. Adding biostimulants also increases soil organic matter, which supplies essential nutrients and further strengthens soil health. For example, biostimulants like mycorrhizal fungi can boost phosphorus availability, improving soil fertility and crop yields. At the same time, seaweed extracts have been shown to improve soil structure and microbial diversity, leading to more resilient, productive soils. This holistic support makes plants more resilient to dry periods and other environmental stresses, providing a sustainable approach to soil management.
Biostimulants and plant health
Some biostimulants also prompt the production of antioxidants and stress-related hormones within plants. Under abiotic stress, reactive oxygen species (ROS) may accumulate, causing oxidative damage. Biostimulants can stimulate antioxidant enzymes, reducing ROS and protecting cellular health. Additionally, they influence stress-related hormones like abscisic acid (ABA), which helps plants conserve moisture by regulating stomatal closure during water stress.
Biostimulants boost plant health by strengthening natural defense systems, enhancing immune responses, and promoting beneficial microbial interactions for biotic stresses from pests, diseases, and weeds. Certain biostimulants contain compounds like chitosan, proteins, and plant hormones that "prime" immune responses, helping plants react more quickly to threats. This priming leads to increased production of defensive chemicals, such as phenolics and phytoalexins, that deter pathogens. Biostimulants also support beneficial plant-microbe interactions to combat biotic stress. They promote the growth of rhizobacteria and mycorrhizal fungi, which form a protective shield around plant roots, limiting pathogen establishment. This microbial community competes with pathogens for resources, reducing disease spread. Altogether, biostimulants help improve plant vigor, making crops more resistant to biotic stressors through stronger roots, better nutrient uptake, and enhanced resilience.
Application and integration of biostimulants
In order to maximize the benefits of biostimulants, they must be applied and integrated into sustainable farming methods. Biostimulants can be applied in a variety of ways, including foliar sprays, which spray the product directly onto plant leaves; soil drenches, which apply the biostimulant to the soil to improve root uptake; and seed treatments, which coat seeds with biostimulants to boost germination and early growth. Biostimulants should be combined with other environmentally friendly practices, such as crop rotation and cover cropping, which enhance soil health and biodiversity to maximize their efficiency. These methods create a more resilient agricultural system by improving soil structure, reducing pest buildup, and supporting nutrient cycling. This integrated approach helps sustain long-term soil fertility and reduces reliance on synthetic inputs, contributing to more sustainable farming practices overall. They can also be combined with cover crops, such as clover, rye, and legumes, to enhance soil structure, prevent erosion, and improve water retention. As these crops decompose, they add organic matter and essential nutrients like nitrogen, supporting soil fertility. Additionally, cover crops attract beneficial insects and microorganisms, promoting natural pest control and soil health for future plantings.
To achieve optimal plant uptake and performance, it is important to carefully follow application guidelines when using biostimulants, including recommendations for dosage and timing. By combining biostimulants with sustainable farming techniques, farmers may improve soil health, raise crop yields, and build more resilient agricultural systems.
Challenges and considerations
For the use of biostimulants in sustainable agriculture to be implemented effectively, several issues and concerns must be considered. Because there are frequently inconsistent rules between different locations, regulatory and standards concerns can make it more difficult to approve and apply biostimulants consistently. Furthermore, the effectiveness of biostimulants can differ significantly based on some variables, including crop type, environmental circumstances, and administration techniques, which might provide uneven outcomes. This unpredictability emphasizes the want for additional study and advancement to comprehend biostimulant systems and maximize their application. Ample training and support are necessary because many farmers may not be aware of biostimulants and their advantages. Another major difficulty is farmer education and adoption hurdles. To ensure that biostimulants are successfully incorporated into sustainable farming methods, lawmakers, researchers, and agricultural educators must work together in a concerted effort to overcome these obstacles.
Future trends and innovations
The future of biostimulants in sustainable agriculture promises significant improvements and breakthroughs. Recent advances in biostimulant formulations and technology, including nanoencapsulation and precision delivery systems, have increased their efficacy and application flexibility, allowing for more targeted and effective interventions. These technological improvements are projected to play a critical role in the development of climate-resilient agricultural practices by increasing plant resilience to environmental challenges, maximizing resource utilization, and enhancing soil health. As new benefits are discovered via research, emerging markets progressively adopt biostimulants, driven by rising awareness and demand for sustainable farming solutions. Global adoption trends show that biostimulants are becoming more widely accepted and integrated into varied agricultural systems, with the potential to revolutionize the future of sustainable agriculture.
References
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Co-Author: Dr Ida Wilson
Specialist in Plant Production/ Industry Consultant
Dr Ida Wilson is a specialist in plant production, with interest in plant protection and plant health. She has a wide knowledge on crop production and crop protection and has served the South African and global plant production industry for more than 20 years. She is a field biologist and is in-field solution driven. She has significantly contributed to the advancement of entire agricultural industries. Her contributions to crop production have been recognized nationally and internationally, and her passion remains to reach a support farmers globally. She believes crop production can drive economic growth and empowerment. It can also support human well-being, creating jobs, which in turn may allow children an education. She has authored more than 200 works on various topics, all with direct value to crop production and aspires to remain a source of advanced and reliable information to farmers.