Thought this might be useful to someone as everything you prob will ever really want to know about silica. Hope I haven't missed anything out.
What Is Silica?
Silica, also known as silicon dioxide, occurs all throughout nature, and none of us would be alive without it. Second only to oxygen, it makes up 59% of the Earth’s crust. On the cosmic scale, it holds the 8th position as the most common element in the universe.
Silica also occurs in 95% of known rocks, and shows up in three main crystalline varieties, including quartz. Every time you go for a stroll on the beach, you make contact with silica with every step, as it, alongside oxygen, works to create sand.
As research expands, growers are realizing the benefits of adding silicic acid, a form of the element silicon, to their growing routines. Silicon is not considered an essential plant nutrient. Still, it provides many benefits to plants. Therefore, some people think of silicon as a biostimulant.
Silicon provides a number of benefits to plants. These include increased resistance to pests and pathogens, increased growth, and increased stress tolerance. The mechanisms behind these benefits vary. Some of these benefits are caused by improved plant responses to pests. Others are due to structural changes in plants. Yet other benefits are caused by changes in plant chemical signaling.
Before you apply silicon, it’s important to understand the forms that plants take up. After all, some forms of silicon are more available to plants than others. Therefore, applying silicic acid, silica, and silicate has different effects on plants. Silicon is everywhere but is generally unavailable to plants. In nature, microbes convert unavailable forms of silicon into (mono)silicic acid – the only (!) bioavailable form of silicon.
Its most common forms silicon is not readily absorbed into biological tissues. Take potassium silicates as an example. Its molecules are too large to penetrate our plants cell walls. Microbes will have to convert it into silicic acid before the roots can take up the silicon. This process is called silicification, and it can take weeks or months before it occurs in any meaningful amount.
For most applications however, speed and bioavailability are critical. Crops are often harvested in a matter of weeks or a couple months, For best results, choose a product that contains mono silicic acid.
Silicon Terminology
Silicon: a chemical element with the symbol Si and atomic number 14
Silica: another name for silicon dioxide (SiO₂); found in the mineral quartz and also a major component of sand
Silicic Acid: a general term for compounds containing silicon (Si), oxygen (O), and hydrogen (H)
Monosilicic Acid: Si(OH)₄ also known as orthosilicic acid
Silicates: compounds containing oxygen and silicon, including calcium silicate and potassium silicate
What Does Silica Do for Plants?
Silicon Promotes Plant Growth
This element increases the growth of cells, leading to faster growth of roots, stems, and shoots. Studies have shown that when growers apply silicon, plants grow taller and have thicker stems. This means stronger both larger and stronger plants. And larger and stronger plants mean higher yields!
Silicon also encourages more lateral branching. So, if you’re looking for taller and bushier plants, add silicic acid. When you apply silicic acid products, you’ll be amazed at how much they impact plant growth.
Improves Resistance to Fungal and Bacterial Pathogens
Although it’s not fully known how silicon helps protect plants against harmful fungi. Some of these fungi include fusarium wilt and powdery mildew. Scientists think one way this element protects plants is by stimulating plant defenses. When you add silicon to your plants, they can better recognize diseases and begin to fight back.
Silicon helps plants fight against fungi such as downy mildew.
Silicon helps plants fight against fungi such as downy mildew.
Another way silicon protects plants is by increasing the production of plant stress hormones. These hormones, including jasmonic acid and abscisic acid, help plants better respond to the stress caused by pathogens.
When you apply mono silicic acid to plants, you can often decrease pesticide applications by 50% or more.
Strengthens Cell Walls
When you apply silicon to plants, it becomes a part of plant cell walls. This leads to an increase in the strength and rigidity of cell walls. Think of silicon as a layer of mortar-enforcing brick walls. The bricks can stand without the mortar, but they are much stronger with it.
With stronger cell walls, plants can better withstand pressure from wind and heavy rain. Since cell walls are less likely to experience damages, plants have a lower risk of breaking stems. Growing your plants indoors in a protected environment? Stronger cell walls still help plants by protecting against abiotic and biotic stressors.
Increases Resistance to Insect Pests
Just like silicon helps plants fight off fungal and bacterial pathogens, it also stimulates plant defenses that protect against insect pests. With these heightened defenses, plants are more likely to win the battles against their attackers.
Once in the plant, this element also stimulates the production of compounds that draw predatory insects and parasitoids in to attack the insect pests. Due to these stronger pest defenses, growers can decrease their pesticide applications.
Improves Tolerance to Drought and Heat Stress
When plants face adverse conditions such as drought, heat, or cold, silicon promotes the production of defense compounds. Along with this, silicon increases nutrient uptake. Therefore, this leads to plants that can better withstand abiotic stressors. Just as with humans, increased health in plants allows them to better respond to trying conditions.
Protects Against Heavy Metals
We know that heavy metals such as cadmium, arsenic, and lead can harm plant health. These metals can damage plant cells, stunt plant growth, and prevent proper nutrient uptake. However, silicon can help protect plants against the damages caused by heavy metals.
One study showed that plants supplemented with silicon can better protect themselves against heavy metal cadmium (Cd). Also, silicon helps protects plants against the harms caused by heavy metal aluminum (Al). Therefore, if you’re growing in contaminated soils, it’s especially helpful to provide your plants with high enough levels of silicon.
Plant Available Silica
Even though silicon is not known as a major nutrient in plant nutrition, it’s quite common in the world. In fact, the earth’s crust contains more than 27% silicon. That makes it the second most abundant element in the earth’s crust, following oxygen.
So, if there is so much silicon already present why must you apply it to plants? Because most of the silicon in the plant’s crust is held in forms plants cannot take up. These include silicon dioxide (silica) and various silicate minerals. Silica is found in nature as quartz, a component of sand, and as a part of other rocks.
While plants can’t take up silica, they can take up another form of silicon —monosilicic/orthosilicic acid. Bacteria can convert other silicon compounds into mono silicic acid. However, this process takes weeks or months. By the time silicon is in a plant-available form, it is often too late. Therefore, growers often apply silicon in the form of mono silicic acid.
What to Look for in Silicon Products
It’s important to take note of not only the percent of silicon in a product but also the percent of plant-available silicon (PAS). Just because a product contains a high percentage of silicon, it does not mean plants will take up a high percentage. Also, just because a product contains stabilized silicic acid, it does not necessarily mean it contains a high amount of plant-available silicon.
When searching for products, look for the form of silicon that a product contains. Next, look for the total silicon content and plant-available silicon content.
Applying Silicic Acid
There are two main ways to apply silicic acid: as a foliar spray or as a soil application.
Research on foliar sprays has shown the following results:
Enhanced root growth
Increased nutrient content
Higher sugar content (Brix)
Decreased bacterial and fungal infections
Increased protein content
Growers can also apply silicic acid to their growing media through a fertigation system. This method also helps stimulate soil bacteria. Therefore, it increases nutrient availability.
Silica During Flowering
While some growers state you should stop silicon applications altogether once flowering starts, plants can benefit from silicon through every stage of their lives. However, they do require less during flowering. So, you can decrease the amount you’re applying.
So, when should you stop using silicon products? There’s no clear answer. Some growers swear by stopping silicon applications once a plant begins flowering. Other growers continue to apply silicon throughout the plant’s whole life. Try experimenting and see what works best for you.
No matter when you stop applying silicon products, make sure you start applying them during early vegetative growth.
Smokey Genetics quote
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Silicic Acid vs. Potassium SilicateIf the plant is loaded in veg shouldn't need it in flower
Potassium silicate (K2SiO3) is a salt of silicic acid (H4SiO4).
As mentioned above, silicates are not available to plants. So, plants cannot take up or use potassium silicate. First, bacteria must convert it to mono silicic acid.
Therefore, applying potassium silicate does not have the same effects as applying mono silicic acid. Plants will not be able to experience the benefits of silicon until weeks or months after you apply potassium silicate.
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