How Silicic Acid Promotes Plant Growth and Stress Resilience

Silicon is one of the most abundant elements on Planet Earth, second only to oxygen. It comprises 60% of the earth’s crust and is present in every soil type in the form of silicates, silicon dioxide, biogenic silica, and silicic acid.
In fact, Silicon is so ubiquitous in soils that, until recently, its role in plant growth and development was taken for granted. But new research demonstrates the power of silicic acid—the plant-available form of silicon—as a powerful plant biostimulant. Silicic acid is increasingly used in agriculture to promote plant growth and protect crops from pests and abiotic stresses.
This blog will help you understand what silicic acid is, how it acts as a plant biostimulant, and how to use it in horticultural and agricultural applications.  

Silicic Acid vs. Silicon: Understanding the Difference

Different silicon components are often referred to as if they are interchangeable, but there are some important chemical differences. Terms that you may see used in the context of silicon in agriculture include: 
Silicon: A chemical element, Silicon (Si) rarely appears in its pure elemental form.
Silicates: Compounds containing silicon and oxygen, like calcium silicate and potassium silicate.
Silica: Another name for silicon dioxide, forming compounds like quartz and sand.
Silicic Acid: Compounds containing silicon, oxygen, and hydrogen. Monosilicic acids (MSAs), also known as Orthosilicic acids (OSAs), are the simplest form of these compounds. They are the only plant-absorbable form of silicon.
Silicon is everywhere, usually in the form of compounds like silicon dioxide and potassium silicate. Soils are rich in these silicon compounds—but they are not bioavailable. The molecules are insoluble or too large to be utilized by plants.
Soil microbes and chemical weather transform these silicon compounds into monosilicic acids in a process called silicification, but this is a gradual process. Silicic acid is then taken up by the roots, transported via the xylem, and distributed within plant tissues. Silicic acid then polymerizes into amorphous silica, strengthening plant cells and tissues. 
Silicon-based fertilizers, like diatomaceous earth and biological silica sources like rice-hull ash, have been used in agriculture to boost levels of plant-available silicon for decades. In the past 20 years, new production processes and technologies have facilitated the creation of stabilized  monosilicic acid amendments. These provide a silicon source that is already bioavailable.
Growers continue to use compounds like silicic acid, but researchers do not classify silicon as an essential element for plant growth. So are silicic acid additives even necessary? And what have they been shown to do?

Evidence of Silicic Acid Efficacy

Silicon compounds may not be essential to plant growth, but they are classified as plant biostimulants in the EU. Although plants can complete their normal life cycle without silicon, they still derive considerable benefits from it.  
The beneficial effects of silicon, especially in the form of silicic acid, are quite remarkable. Research has demonstrated that stabilized silicic acid amendments can:

 

Other silicates are beneficial and improve plant resilience to abiotic and biotic stresses, but they do not seem to affect plant growth and development. Stabilized silicic acid is the only silicon compound that improves stress resilience and boosts crop performance and yields.

Silicic Acid Use in Agriculture and Horticulture

So, why does silicon have such a beneficial effect on plants? Research has established the mechanisms behind plant uptake and transportation, but it is still not clear exactly how silicon influences cellular and metabolic processes.  
Despite the pathways behind the beneficial effects of silicon being unclear, dozens of studies have demonstrated that silicon deprivation inhibits plant growth, development, viability, and reproduction. Without enough bioavailable silicon, plants are structurally weaker and more susceptible to biotic and abiotic stresses.
The use of silicon compounds in agriculture began in the early 1990s as we began to understand the influence of silicon on plant health. Potassium silicate and sodium silicate applications helped reduce infections like powdery mildew, rice blast, and soybean rust. 
In the early 2000s, new production processes made the stabilization of monosilicic acids possible. The application of silicon in its only bioavailable form accelerates plant absorption and significantly improves growth and development—benefits that traditional silicate amendments do not provide. Silicic acid can improve not only yields, but other quality traits like flavor, color, and aroma to add further value to specialty crops like cannabis. 
The highly concentrated form of bioavailable silicon means far lower quantities are needed compared to other silicates. Silicic acid lowers application rates and frequencies, making it a cost-effective and effective biostimulant for growers at any scale.

How to Use Silicic Acid as a Plant Biostimulant

Stabilized monosilicic acid products, like Impello’s Dune™ formulation, can be used as a foliar spray, hydroponically, or as a soil amendment. Some studies suggest that foliar application is the most effective, but it can also be added to the root zone as part of your hydroponic solution or fertigation system. 
For foliar applications, apply at least 1-2 times during vegetative growth and 1-3 times during flowering. Weekly applications at low to medium rates are ideal for most crops. 
For fertigation & root zone applications, apply at least 2-3 times during vegetative growth and 2-4 times during flowering. Weekly applications at low to medium rates are ideal for most crops.  
Adding silicic acid to your nutrition program is a sustainable, cost-effective way to boost yields and improve plant resistance to biotic and abiotic stresses, perfect for horticulturists seeking optimal performance for fast-growing annuals and high-value specialty crops.
To learn more about silicic acid, check out our Impello Dune™ formulation. Taking its name from silica-rich desert sands, Dune™ reimagines what silicon can do for plant growth. You can also drop us a line at tech@impellobio.com! We’re endlessly passionate about making horticulture better and would be eager to answer any questions you have about adding silicic acid and other plant biostimulants to your nutrition program.
To dive deeper into silicic acid use for agriculture, here are the references cited in this blog:
Abayisenga, J. C., Mbaraka, S. R., Nkurunziza, C., Shema, M. J., Murenzi, F., Rucamumihigo, F. X., Habimana, S., Persson Hovmalm, H., Neeru, J., Rushemuka, P., Cyamweshi, A. R., & Ndikumana, I. (2022). Effect of Soil Application of Stabilized Ortho Silicic Acid Based Granules on Growth and Yield of Rice (Oryza sativa L.). Communications in Soil Science and Plant Analysis, 1–9. https://doi.org/10.1080/00103624.2022.2112593
Alyousuf, A., Hamid, D., Desher, M. A., Nikpay, A., & Laane, H. M. (2021). Effect of Silicic Acid Formulation (Silicon 0.8%) on Two Major Insect Pests of Tomato under Greenhouse Conditions. Silicon, 14(6), 3019–3025. https://doi.org/10.1007/s12633-021-01091-7
Dwivedi, S., Kumar, A., Mishra, S., Sharma, P., Sinam, G., Bahadur, L., Goyal, V., Jain, N., & Tripathi, R. D. (2020). Orthosilicic acid (OSA) reduced grain arsenic accumulation and enhanced yield by modulating the level of trace element, antioxidants, and thiols in rice. Environmental Science and Pollution Research, 27(19), 24025–24038. https://doi.org/10.1007/s11356-020-08663-x
Laane, H. M. (2016). The Effects of the Application of Foliar Sprays with Stabilized Silicic Acid: An Overview of the Results From 2003-2014. Silicon, 9(6), 803–807. https://doi.org/10.1007/s12633-016-9466-0 
Laane, H. M. (2018). The Effects of Foliar Sprays with Different Silicon Compounds. Plants, 7(2), 45. https://doi.org/10.3390/plants7020045
Luyckx, M., Hausman, J. F., Lutts, S., & Guerriero, G. (2017). Silicon and Plants: Current Knowledge and Technological Perspectives. Frontiers in Plant Science, 8. https://doi.org/10.3389/fpls.2017.00411 
Ma, J. F. (2003). Functions of Silicon in Higher Plants. Silicon Biomineralization, 127–147. https://doi.org/10.1007/978-3-642-55486-5_5
Shwethakumari, U., & Prakash, N. (2018). Effect of Foliar Application of Silicic Acid on Soybean Yield and Seed Quality under Field Conditions. Journal of the Indian Society of Soil Science, 66(4), 406. https://doi.org/10.5958/0974-0228.2018.00051.8
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