How Silicic Acid Promotes Plant Growth and Stress Resilience

Silicon is one of the most abundant elements on 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 (found in living organisms) 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 research increasingly demonstrates how silicic acid—the most plant-available form of silicon—can act as a powerful plant biostimulant. Silicic acid is being more frequently used in agriculture to promote plant growth and protect crops from pests and abiotic stresses. But also, in recent years, the more we learn about silica, the more we learn that different plant species have very different relationships with silica, and the more you know, the better you can optimize this amazing nutrient for your crop.

This blog will help you understand what silicic acid is, how it acts as a plant biostimulant, how to use it in horticultural and agricultural applications, and what you may need to consider when doing so.

What are some of the different forms of silica?

Different silicon-based compounds 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: An individual chemical element, Silicon (Si) rarely appears in its pure elemental form.

Silicates: Compounds that contain silicon and oxygen, like calcium silicate and potassium silicate.

Silica: Another name for silicon dioxide; composes the major part of compounds like quartz and sand.

Silicic Acids: Compounds that contain silicon, oxygen, and hydrogen. Monosilicic acids (MSAs), which are also known as Orthosilicic acids (OSAs), are the simplest commercialized form of these compounds. To date, these are the only plant-absorbable forms of silicon, though, in 2024 as nanotechnology is increasingly being put to use in agriculture, silicon nanoparticles are being suggested as another route of formulating plant-available 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 either insoluble or too large to be utilized by plants in those forms.

Soil microbes and chemical weathering transform these silicon compounds into monosilicic acids, but this is a gradual process. Once in these simpler forms, silicic acids can be incorporated into plant tissues in a process called silification. Silicic acids are taken up by the roots, transported via the xylem, and distributed within plant tissues. Silicic acid then polymerizes into the silica structures known as phytoliths, which are part of what strengthens plant cells and tissues and make silica-treated plant tissues unattractive to pests and pathogens.

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. But 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 yet be classified as essential to plant growth (though we disagree if your goal is growing the healthiest plants possible!) but they are classified as plant biostimulants. Although plants can complete their normal life cycle without silicon, they still derive considerable benefits from it and suffer consequences without 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:

• Enhance crop yield, quality, and plant and root growth
• Promote resilience to abiotic stresses like heat and drought
• Work against pests, reducing insect pest populations and rates of bacterial and fungal infections
• Regulate the uptake  of other plant nutrients
• Reduce plant accumulation of toxic heavy metals

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 this, 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.

Routine use of silicon compounds in agriculture took hold in the 1990s as we began to truly 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 this, 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 fruits or cannabis. Also, silicic acids can be highly concentrated in bioavailable form, so means that far lower quantities are needed compared to other silicates. Silicic acid lowers application rates and frequencies, making it a cost-effective and yield-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. Increasingly, we are aware that some plants see more benefit than others through different application modes, so it is good to be aware whether there is data to suggest that your crop species is a known accumulator or non-accumulator as this may impact the ability the plants have to effectively uptake silicon compounds through the root 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

Yan G, Huang Q, Zhao S, Xu Y, He Y, Nikolic M, Nikolic N, Liang Y and Zhu Z (2024) Silicon nanoparticles in sustainable agriculture: synthesis, absorption, and plant stress alleviation. Front. Plant Sci. 15:1393458. doi: 10.3389/fpls.2024.1393458

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