Silica-containing fertilizers aid in mitigating drought stress, resistance to mineral stress, and improve overall plant strength and growth. Cannabis growers can utilize silica fertilizers from day one of production to strengthen plants from beginning to end. This tech tip will explore some best practices for how to apply one such product, AgSil 16H.
AgSil 16H from Certis and other silica products require some special consideration to achieve the best application. Silica and silicate products need to be solo-injected from designated stock tanks and never tank mixed with other nutrients. Mixing highly concentrated silica products with nitrates and sulfates can lead to the formation of precipitates, which can clog lines, drippers, or filters. AgSil 16H and other silica products should ideally be injected first into the irrigation lines, before other fertilizers. It’s always a good idea to include a mixing chamber following silica injection to allow full dilution. Once fully in solution at ready-to-use concentrations, silica and other nutrients are totally compatible.
A final important consideration is pH. For many silica products, AgSil 16H included, a pH between 5.5-6.5 results in a gelling of silica when highly concentrated. Growers can either adjust stock solution pH down to between 4-5, or target between 7-8 to avoid this issue. First add AgSil 16H to water to fully dissolve, then slowly add diluted acid with mixing until the desired pH range is reached. If gelling occurs, agitate and slowly add acid until gelling has dissipated.
AgSil 16H contains 53% silica and 32% potassium. It is best applied as a once or twice weekly drench at 1.28-2.56 oz per 100 gallons to provide 50-100 ppm Si. While grasses and other silica accumulators would likely prefer 100 ppm, Cannabis has demonstrated good responses to the 50 ppm rate. Constant injection should target around 10 ppm Si, at 0.256 oz per 100 gallons. AgSil 16H can also be applied as a foliar spray, at a rate of 1-2 lb per 100 gallons. Try adding CapSil at 8 oz per 100 gallons for improved spreading over foliage.
