Silicon is recently becoming recognized as a beneficial plant nutrient and many growers already include it in their crop fertility programs.

DEFINITION

Silicon—the second-most abundant chemical element in the earth’s crust after oxygen—is denoted by the symbol Si. 

Though it makes up twenty-eight percent of the planet by weight, pure silicon is rare: most of the silicon in the earth’s crust is bonded with oxygen. This brings us to our next two terms.

Silica or silicon dioxide (SiO2), or silicate minerals are the forms in which the earth’s silicon is most likely to be encountered: these are combinations of the elements silicon and oxygen, in different balances.

Ninety percent of the earth’s crust is comprised of these compounds. Commonly-known examples are quartz, agate, onyx, jasper, vermiculite, tac, and feldspar. 

Silicone describes a group of rubber-like polymers, which are more likely to be a part of agricultural machinery than crop nutrients.

THE ROLE OF SILICON IN PLANTS

Now that the terms are clear, it is easier to get down to the nitty-gritty of the role of silicon in plant nutrition and agriculture.

It is what plant biologists call a “non-essential beneficial plant nutrient,” meaning that you don’t need to apply it to your crops like nitrogen, phosphorus, and potassium (NPK), but doing so can provide many benefits for both monocots (grasses, onions) and dicots (leafy greens, legumes).

 It is known that silicon plays a role in reinforcing the cell wall of plants, and it is speculated that because of this is may aid in giving plants increased resistance to pests and diseases, increased tolerance to drought and heavy metals, as well as increasing both crop quality and yields.

Cucurbit (cucumber, pumpkin, gourd) growers, for example, will often add a form of silicon to irrigation water to increase the plant’s resistance to powdery mildew:

the mechanism by which this works is thought to be by strengthening the leaf cell walls of the plant against fungal spore invaders in intercellular spaces, and also by increasing the permeability of the plant’s roots to water, making them more resistant to drought stress that encourages the progression of disease.

FORM AVAILABLE TO PLANTS

The form of silicon that is available to plants as a nutrient is called monosilicic acid (H4SiO4). The availability and amount of this compound is influenced by other parts of the soil makeup, including pH, the presence of clay, organic matter, and iron (Fe) or aluminum (Al) oxides/hydroxides.