Biostimulants: A Tool for a More Conscious Agriculture
The context of biostimulants:
Nowadays, agriculture is an activity that faces many problems. First, with the pressure of climate change (decreased yields) and an ever-increasing population, agricultural production’s major challenge is ensuring food security, especially after recovering from the global COVID-19 pandemic (FAO, 2023).
Confronted with this situation, we must double food production by 2050 (Singh et al., 2024). Farmers use products with different chemical compositions that affect the environment and the plants to achieve this goal. However, biostimulants offer an alternative and environmentally friendly solution to make agriculture more sustainable and efficient. (Singh et al., 2024)
What are biostimulants?
The first question that pops up in our minds when we hear about biostimulants is, what are they? Numerous authors have recently been interested in answering this question. The term biostimulants appeared in 1933, and it has been given many definitions throughout the years, such as the following: (Yakhin et al., 2017)
– « Plant hormone-containing substances that can stimulate growth when exogenously applied » (Schmidt, 1992)
– « Product generally of organic nature which increases the soil microbial activity and/or plant growth » (Nardi et al., 2006)
– « Materials that are neither a fertilizer nor a pesticide, but when applied to a plant will enhance their health, growth, and protection. » (Banks et Percival, 2012)
If we look at these definitions, we can see that the authors focused on defining biostimulants by eliminating confusion with other products. Biostimulants are neither fertilizers, pesticides, nor nutritional additives.
Their main role is to enhance plant health and growth/vigor.
The AFNOR (French Standardization Association), in their recent document published in April 2022, defines biostimulants as: “Products that stimulate the plant’s nutritious process independently of the nutrients it contains, with the sole purpose of improving one or more of the following characteristics of plants or their rhizosphere:
– Nutrient utilization efficiency
– Tolerance to abiotic stress
– Quality characteristics
– The availability of nutrients confined in the soil or rhizosphere.” (AFNOR, 2022)
What are the differences between biostimulants and biocontrols?
It is pretty common to confuse these 2 products. Biostimulants act on abiotic stress such as drought, excess/use of water, extreme temperatures, salinity, and mineral deficiencies. Biocontrol agents act against biotic stress like diseases, insects, and parasitic plants. (Académie des biostimulants, s. d.)
Figure 1: Biostimulants protective effects against abiotic stress. By Oosten, Pepe, Pascale, Silletti, Maggio – https://commons.wikimedia.org/wiki/File:Graphical-abstract-Biostimulants-have-protective-effects-against-abiotic-stress.gif
What is the origin of the active ingredients of biostimulants?
According to their origin, there are 5 different sources: (UNIFA, 2023)
– Animal: amino acids
– Plant: algae extract, betaine, amino acids
– Microbial: bacteria, fungi, yeast, microorganism extracts
– Mineral or mineral extracts: silica, humic substances
– Synthetic: hormone precursors, folic acid, lignosulfonate.
Even though it is important to acknowledge the origin of the active ingredients, we need to focus on the performance and effectiveness of biostimulants.
How can biostimulants be used?
There are 4 different modes of application of biostimulants: (UNIFA, 2023)
– Soil application
– Foliar application
– Seed treatment
– In combination with a conventional fertilizer or phytopharmaceutical products
How efficient are biostimulants?
The efficiency of biostimulants relates to their mode of application and their origin. With the system of opening and closing of the stomata on the leaves, plants can absorb nutrients through their leaves more efficiently than through their roots. That makes foliar applications more efficient, making nutrients more easily accessible to the plants. That will also speed up their function (K.V.Supraja et al., 2020).
Moreover, when it comes to their composition, biostimulants act on different parts: Seaweed extract is known for being highly nutritious when it comes to the essential macro and micronutrients (Zheng et al., 2022).
The efficacy of microalgal extracts as seed treatment and foliar spray applied in tomato plants has shown an improved germination efficiency, based on research results (K.V.Supraja et al., 2020)
In another study, it has been proven that using biostimulants in plants for flower production positively affects both the quantity and quality of the flowers (Vinutha et al., 2017). This phenomenal performance of seaweed extracts is explained by the fact that macroalgae contain many plant growth hormones such as auxins, abscisic acid, cytokinins, and gibberellins (Oancea et al., 2013).
In addition, algae contain an essential compound for plant growth, carrageenan, which has been reported to increase plant growth and the defensive reaction against infections when applied to various plant species. (Md. Motaher et al., 2024)
Biostimulants against herbicide stress:
Herbicides are used to eliminate weeds, but due to their chemical composition, they can cause damage to plants if misused (Grandel, 2024). Such uncautious use can be an excessive dose, selectivity problems of the herbicide on the crop, or even when the herbicide is applied under inadequate weather conditions leading to toxicity problems (biostimulant.com, 2020).
This stress can be observed as delayed growth and development of the plant, as well as leaf chlorosis and necrosis, leaf deformation and abnormal growth, root damage and impaired nutrient uptake, reproductive abnormalities, and physiological stress and water imbalance (Grandel, 2024). This stressful situation impacts the plant’s overall performance.
Against this stress, some biostimulants can help by intensifying the release of stress alert messengers in the plant cell so that the crop’s enzymatic metabolism can be activated, which eliminates the toxic compounds from cells. Thus, photosynthesis and growth can restart. (Aladin.farm, 2023)
Based on this, we can say that there’s a need to identify systems with combinations of plant species, biostimulants, and herbicides as a response to the fact that biostimulants protect crops from herbicide injuries and creating a new and innovative agricultural technique, improving both the crop production and plant’s performances (Nikolaos et al., 2023).
Figure 2: Herbicide stress symptoms on wheat. (IRIIS phytoprotection, s. d.)
References:
Académie des biostimulants. (s. d.). Distinction avec le biocontrôle. Académie des Biostimulants. [Consulté le 2024-04-11]. http://www.biostimulants.fr/produits-utilisation/definition/distinction-biocontrole/.
AFNOR. (2022). Biostimulants des végétaux -Allégations- Partie 1: Principes végétaux
Aladin.farm. (2023). Stressé par le désherbage ? Ayez le réflexe « detox » avec Agroptim SUNSET ! | Aladin.farm. [Consulté le 2024-03-08]. https://www.aladin.farm/article/stresse-par-le-desherbage-ayez-le-reflexe-detox-avec-agroptim-sunset-olmix-publie-fournisseur.
Banks J., Percival G. (2012). Evaluation of biostimulants to control Guignardia leaf blotch (Guignardia aesculi) of horsechestnut and black spot (Diplocarpon rosae) of roses. http://www.ncufc.org/uploads/biostimulantsanddisease.pdf
biostimulant.com. (2020). Blog 37 L’application de biostimulants atténue le stress dû aux herbicides dans le tournesol. Biostimulant.com. [Consulté le 2024-03-08]. https://www.biostimulant.com/fr/blog-37-biostimulant-application-mitigates-herbicides-stress-in-sunflower/.
FAO, FIDA, OMS, PAM, UNICEF. (2023). L’État de la sécurité alimentaire et de la nutrition dans le monde 2023. : FAO; UNICEF; IFAD; WFP; WHO; http://www.fao.org/documents/card/fr/c/cc3017fr
Grandel D. (2024). Herbicide Stress. OMEX. [Consulté le 2024-03-08]. https://omexcanada.com/blog/herbicide-stress/.
IRIIS phytoprotection. (s. d.). Phytotoxicité-Herbicide du groupe 2. IRIIS phytoprotection. [Consulté le 2024-04-30]. https://www.iriisphytoprotection.qc.ca/.
K.V.Supraja, Bunushree B., P. Balasurbamanian. (2020). Efficacy of microalgal extracts as biostimulants through seed treatment and foliar spray for tomato cultivation
Md. Motaher H., Farjana S., Sabia K., Jannatun N., Mahabuba M., Humayra F., Laom-Son P.T., Mohammad Golam M. (2024). Carrageenans as biostimulants and bio-elicitors: plant growth and defense responses
Nardi S., Ertani A., Concheri G., Pizzeghello D. (2006). Metodi di determinazione dell’attivita biostimolante. http://fertilitasagrorum.ciec-italia.it/index_file/volumi.htm
Nikolaos K., Panagiotis S., Sofia V., Dimitrios L., Aspasia E. (2023). Application of Biostimulants and Herbicides as a Promising Co-Implementation: The Incorporation of a New Cultivation Practice
Oancea F., Velea S., Fatu V., Mincea C., Ilie L. (2013). Micro-algae based plant biostimulant and its effect on water stressed tomato plants. Romanian Journal of Plant Protection, vol. 6, p. 104‑117
Olmix. (s. d.). Plante Care. Olmix, https://olmix.com/plant-care/
Schmidt, R. E. (1992). Biostimulants. Grounds Maintenance 1992. 27, 38–56.
Singh R., Kaur S., Bhullar S.S., Singh H., Sharma L.K. (2024). Bacterial biostimulants for climate smart agriculture practices: Mode of action, effect on plant growth and roadmap for commercial products. Journal of Sustainable Agriculture and Environment, vol. 3, n. 1, p. e12085
UNIFA. (2023). Le marché des biostimulants: Stimuler la vie des plantes. https://www.unifa.fr/sites/default/files/2023-02/biostimulant-unifa-vf-fevrier-2023-mail.pdf
Vinutha D.B., Hemla Naik B., Chandrashekar S.Y., Thippeshappa G.N., Kantharaj Y. (2017). Efficacy of Biostimulants on Growth, Flowering and Quality of China aster cv. Kamini
Yakhin O.I., Lubyanov A.A., Yakhin I.A., Brown P.H. (2017). Biostimulants in Plant Science: A Global Perspective. Frontiers in Plant Science, vol. 7. http://journal.frontiersin.org/article/10.3389/fpls.2016.02049/full
Zheng W., Rui Y., Ying L., Shulan Z., Zejin Z., Chaouhua S., Jing L., Zhiyong Q., Qichang Y. (2022). Comparing Efficacy of Different Biostimulants for Hydroponically Grown Lettuce (Lactuca sativa L.)
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