Silicon (chemical symbol = Si) is the 14th element in the periodic table and is listed within the carbon group along with carbon (C), tin (Sn) and lead (Pb). Pure silicon is a metalloid of crystal-like appearance with a blue-gray metallic luster. Silicon
represents about 28% of the Earth’s crust on a weight basis and is the second-most-abundant element on Earth (oxygen is the first).
Silicon is rarely found alone in nature, as it typically exists in the form of silicon dioxide (SiO2) and is referred to as “silica.” Many soil minerals and clays are composed of silica and related substances, and weathering of aluminosilicates
is a source of dissolved silica for plant uptake.
Sand is composed of quartz (a silicate mineral), and silica has many industrial uses, including ceramics, glass, porcelain, Portland cement, synthetic polymers and more. Today, the “Information Age” or “Digital Age” is also known
as the “Silicon Age” because of its use in semiconductors, transistors and especially integrated circuit chips used in computers and smartphones.
Recently, Elizabeth Guertal, Ph.D., (formerly Auburn University, currently at Kansas State University’s Feed the Future Innovation Lab for Collaborative Research on Sustainable Intensification) and Lawrence Datnoff, Ph.D., (Louisiana State University)
conducted an extensive review and analysis of silica use in turfgrass management. Their investigation focused on research of silica associated with plant disease, wear tolerance and abiotic stress.
Silica and disease
Silica has been shown to reduce the occurrence and severity of some turfgrass diseases, such as gray leaf spot (Pyricularia grisea) of perennial ryegrass (Lolium perenne) and St. Augustinegrass (Stenotaphrum secundatum); dollar spot
(Clarireedia jacksonii) of creeping bentgrass (Agrostis stolonifera); and powdery mildew (Erysiphe graminis) of Kentucky bluegrass (Poa pratensis). In those studies, silica was applied in the form of calcium silicate (CaSiO3), calcium/magnesium silicate
(Ca/MgSiO3) or potassium silicate (K2SiO3). However, silica application rates needed to achieve effective disease reduction and management are considered high at 8 to 50 pounds per 1,000 square feet (391 to 2,441 kilograms per hectare). Also, disease
control varied with turfgrass species, soil type and soil silica content, and desirable turfgrass quality was not achieved without additional use of fungicides. More research is needed to investigate silica’s role with plant defense mechanisms
and pathways.
Silica and wear tolerance
The story with wear tolerance is that silica can “harden” leaf blades and therefore improve the “toughness” of the turfgrass sward. A few studies evaluated the use of silica to improve turfgrass wear
or traffic tolerance but had mixed or inconclusive results. More research is needed to evaluate the potential for silica uptake and accumulation into turfgrass tissues from foliar and soil drench applications. However, a recent study did show that
silica applications improved perennial ryegrass density in the presence of traffic. What about green speed? The notion that silica applications can “stiffen” leaf blades and therefore increase golf ball roll is largely anecdotal, with
no published scientific research currently available on this subject.
Silica and abiotic stress
This topic has been studied with some agricultural crops, and there are few studies on turfgrasses. In a growth chamber experiment with Kentucky bluegrass seedlings, higher silica application rates were associated with increases
in leaf area and leaf blade length. Also in that study, sodium concentration in roots decreased, leading investigators to conclude that silica inhibited the absorption and transfer of sodium. In greenhouse experiments, foliar applications of silica
improved drought stress of creeping bentgrass; soil-incorporated silica improved drought stress of St. Augustinegrass; and silica applications to Kentucky bluegrass increased photosynthesis and leaf water content during imposed drought stress. More
research on silica applications and abiotic stress management is needed under field or “real world” conditions.
Research also is needed to help soil testing laboratories identify the best soil extractant for measuring soluble silica and to determine the optimum amount of silica required for different soil types and turfgrass species. More research also is needed
to examine and confirm opportunities for silica to effectively prevent or mitigate abiotic and biotic stresses to turfgrass.
Source: Guertal, E.A., and L.E. Datnoff. 2021. Silicon in turfgrass: A review. Crop Science 61:3861-3876 (https://doi.org/10.1002/csc2.20591).
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 21-year member of GCSAA.