By Chris Kehoe

Silica is widely misunderstood. It is mistakenly left out of most plant nutrition and agriculture input management programs. Current popular wisdom for adding silica (SiO2) to any cannabis nutrient regime is relatively limited to strengthening cell walls and increasing vigorous plant growth. Fortunately for growers who are ready to master the art and science of cannabis cultivation, the role of silica is just now being discovered for optimizing success in plant nutrient programs. 

Modern plant science classifies silica as a beneficial micronutrient required for healthy plant growth. Silica is a naturally occurring compound containing the elements Silicon (Si) and Oxygen (O), known scientifically as silicon dioxide [SiO2]. In order for plants to benefit from SiO2, silica must be plant available in forms such as silicic acid [Si(OH)4] or Monosilicic acid [H4SiO4]. 

Historically, most soils had some soluble forms of silica as a result from physical and geochemical weathering. Due in part to climate change and unsustainable farming practices, plant-available silica in native soils is increasingly rare. Today most commercial agriculture-grade silica fertilizers are byproducts of industrial steel production. 

With more cannabis growers required to follow strict SOP (Standard Operating Procedures), it is important to source clean and green inputs. Naturally derived silica products available for sustainable farming practices are derived from fermented plants (such as horsetail), volcanic mineral deposits, and those that are mined from ancient mineral sea beds, commonly known as diatomaceous earth.

Applications to various agricultural crops indicate silica accumulates in plants at different rates and is critical for many physical and biochemical functions. Cannabis uses silica at every stage of growth. Once taken-up by the plant, silica will not only strengthen the xylem and vascular transport network, but will act as a bio-regulator of other minerals and micro-nutrients. 

Plants with access to silica will better control the uptake of a host of essential nutrients, including phosphorus, by increasing the ability to deliver the most critical foods at every stage of growth. Activation of this uptake control in plants will also help mitigate certain non-beneficial toxins and heavy metals from entering the rhizosphere. 

Studies have shown a connection between adequate silica and reduced fungus diseases such as fusarium wilt. In the case of powdery mildew, disease attack has been shown to reduce the impact on flowers, coffee and grapes treated with silica. Silica also reduces manganese toxicity common in acidic soils that cause brown spots, leaf desiccation, and reduced plant growth.

Consider silica the new “smart drug” for plant health. Increasing size and physical strength are obvious benefits that all plant-lovers can appreciate. Increasing the ability to regulate the uptake and translocation of essential plant nutrients is even more impressive. 

Experienced growers understand the many challenges to growing exceptional quality cannabis. The knowledge and ability to quickly identify specific biotic and abiotic stressors reduces critical time to remedy potentially devastating problems. When plants are deficient in silica the immune system is compromised and a weakened plant will be susceptible to diseases, pests and dangerous pathogens. 

Protecting valuable crops from pests requires a rigorous IPM (Integrated Pest Management) program. One line of defense from many pests is simply the strengthening of plant tissues. There are many studies showing how silica will help the plants resist attacks from certain herbivorous insects because they are unable to chew on hardened tissues. This physiological resistance is also catalyzed by the production of phytochemicals such as tannic and phenolic compounds. Science has shown that most pests are unlikely to attack a healthy plant with these naturally occurring compounds. 

For outdoor growers silica helps protect crops from excessive heat, cold and wind stress. Strong plants will have fewer broken branches and are better prepared to handle the weight of heavy flowers. 

Another lesser known function is in the role in photosynthesis. Studies have shown leaves with sufficient amounts of silica capture sunlight more efficiently by tracking the movement of the sun, thus maximizing the phytochemical producing photoperiod, and contributing to increased plant growth.

It is often noted in scientific journals the use of silica in many crops will increase biomass, flower weight and oil production. In one recent side by side study, resin oil content and terpinoid profiles were significantly boosted. In this case, the grower used the same grow media, the same genetics, and added silica as the only new input to the standard nutrient program. Lab tests confirmed the increase of THC resins in each of the genetic profiles. Although more data is needed to substantiate this finding, this result alone could be a game-changer for cultivators in an ever competitive cannabis landscape.

Of the silica-based fertilizers available to growers it is important to distinguish the pros and cons of each. Many commercial-scale flower producers apply silica in a foliar spray. This application methodology does not allow important Monosilicic acids to be absorbed by the roots, systemically into the plant, and will not provide the same benefits that micronized silica rock dusts can. For hydroponic growers, using soluble forms of silica in nutrient solutions will help maintain a disease-free grow environment while giving roots access to the multitude of benefits.

Minerals such as Azomite™, Greensand, and Glacial Rock Dust contain various amounts of silica and have been relatively successful in the maintenance of healthy gardens. Although many farmers also use Diatomaceous Earth for its silica content, the hardened mineralized diatoms are slow to break down and may take years before plants can benefit. Volcanically derived mineral clays, such as Silica Earth™, is made up of micronized particles that can easily be broken down for increased bio-availability. 

Remineralizing soils is an essential practice for sustainable food and flower production. Minerals will not only help sequester carbon from the atmosphere, but add important nutrients back into the soil food web. Silica, once a neglected mineral nutrient, is now emerging as an integral part in any proactive cannabis plant and soil care program.