Silicon is the cement that that binds the cell in plants. Once deposited it is immobile, so it’s important to continuously supplement with Si throughout the entire growth cycle. Si can provide beneficial supplementation; increasing size, strength along with pest and disease resistance. It can also preserve moisture content and weight during storage and transport.
Si supplementation can improve growth, yield and overall health.
- Improves photosynthesis and raises brix in all plants.
- Reduces excess levels of aluminum, sodium and manganese and iron.
- Improves plant growth, lifting yield and quality.
- Improves pollination and increases pollen fertility.
- Produces a tough outer cell wall resulting in stronger, more resilient plants.
- Reduces fresh weight loss during storage and transportation.
What Is Silicon?
Silicon is the second most common element in the earth’s crust. It is found as sand (silicate dioxide) and more commonly as sheet silicates. These are compounds containing silicon, oxygen and an additional metal or mineral and there are literally hundreds of different variations of them forming over 90% of the earth’s crust.
Silicon leaches from the crust’s sheet silicates and becomes available to plants as mono-silicic acid. Ground water absorb by plants can contain around 400 ppm of silicic acid. Tissues samples taken from plants grown in soil show a Silicon content of up to 10% of dry weight. In some cases, Silicon can be found at the same % as calcium, magnesium and phosphorus. Some grasses may contain Silicon at a higher % than any other mineral.
While Silicon is not considered an essential element for plant growth, there is a strong argument that it should be considered as a relevant macro-nutrient because it is found in such abundance in plant tissues.
How Do Plants Use Silicon?
Plants absorb Si in the form of monosilicic acids. In hydroponic applications, the most common form of Si is as a Potassium Silicate (K2O3Si) additive.
After uptake, Si is transported to required sites and is deposited as either hydrated silicon dioxide (SiO2 · nH2O) to store water molecules the plant between the plant cells or as silica within the walls of the individual plant cells.
Si acts as the mortar between bricks in the cell walls or between the actual cells themselves. It increases the structural integrity of the plant, making stems and branches thicker and stronger, and leaves greener and tougher.
Benefits of Supplementation
Si supplementation can improve growth, yield and overall health.
Improved Plant Cell Development – Increasing Si availability will increase silica deposits in the cell walls. After uptake, Si is permanently deposited into the cell walls. These deposits form a silica-cellulose framework that is stronger built faster than without the inclusion of Silicon. Plants develop faster and grow quicker with Si availability.
Balancing Uptake Of Elements – Silicon in the nutrient solution can positively affect the uptake and absorption of several macro and micro nutrients. Silicon increases Zinc uptake; an essential element in growth and photosynthesis. Silicon increases the availability of Nitrogen to the plant as its application (in soil) will reduce the loss of Nitrogen to Ammonia (a naturally occurring process in soil). Silicon also balances the uptake of Phosphorus, reducing the risk of P toxicity in the plant.
Protection Against Metal Toxicity – Increasing Si availability will prevent metal toxicity. Si competes at the root zone for uptake against certain metal elements including: Aluminum, Manganese and Iron. While these are essential for growth, excesses of these elements can be problematic. Si deficiency in the root zone can lead to uptake levels of these metal elements to toxic levels. While difficult to diagnose, Si deficiency can be very detrimental to yield.
Maintain Cell Integrity and Plant Strength – Increasing Si availability will help plants become visibly stronger, with wider, thicker stems and branches. Si deposited in cell tissue increase structural integrity, helping the plant resist xylem and phloem compression during drought and extreme heat. Stronger xylem results in more rigid and turgid leaves for better light interception. Wider stems and branched corresponds to more uptake and transpiration of water and nutritional elements. So, in theory the plants can grow bigger and at a faster pace. Also, thicker branches are able to hold more weight without the need of additional support, giving the plant body and structure.
Protection Against Pests and Disease – Si deposited in the cell walls toughens the outer skin of the plant, making it more difficult for pathogens to penetrate into the plant and become a systemic problem. When a plant is attacked by a pathogen such as powdery mildew or pythium, the plant will transport and deposit any Si to the area of attack. This stimulates the production of anti-fungal flavonoids that halt the infection process. Si is deposited in the epidermal cells and endodermis of the roots forming a tough physical barrier against fungal and nematode attack.
Overall Increase In Weight And Bulk – Plants grown with Si supplementation have leaves that are darker green, increasing their potential for photosynthesis and better growth. This, together with wider, stronger branches and stems and resilience to disease and pests will ultimately lead to bigger yields.
Si is immobile after it is deposited so continued supplementation is required throughout the entire growth cycle.
Usually Si is not included in standard two or three part nutrient concentrates or root and bloom stimulators. For Si to stay soluble, it requires a high pH – greater than 7.0. When included in regular hydroponic nutrient concentrates, it reacts with other elements, causing potential nutrient deficiencies. As a regular supplement using soluble silicate additives, Si can mix with a regular nutrient solution and be supplied to the root zone. Also, Si can also be applied as a foliar spray using soluble silicate additives. Si supplementation can be done separately from the basic nutrient mix can prevent chemical reactions and ensure optimal dosing.
Growing Without Silicon
When plants are grown without Si, they may be structurally weaker than plants grown with supplemental Si.
- Increased stalk and or root lodging (bending of the stalk or entire plant) caused by weaker mechanical structural and lower structural integrity.
- Increased vulnerability to attack from pathogens, nematodes and other pests.
- Increased vulnerability to toxic metals that tend to build up in the root zone.
Several articles discuss the importance of Si as a supplemental nutrient. Among those reviewed for this article:
Dr. Mary Provance Bowley, Ph.D, Silicon’s Beneficial Effects in Greenhouse Production: March 2015;
Sonali Jana and Byoung Ryong Jeong; Silicon: the most under appreciated Element in Horticulture Crops; Trends in Horticulture Research; 2014.
Galati, Marques, Morgado, Muniz, Filho and Mattiuz; Silicon in the turgidity maintenance of American Lettuce; African Journal of Agricultural Research; 2015