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Dr. Mark Howieson, Product Development Specialist, Becker Underwood Inc. discusses silicon amendments for stronger, more stress resistant turf


SILICON (Si) I


nterest in the use of silicon as a plant growth supplement has increased recently within the turfgrass industry. This is fuelled by emerging evidence that regular applications of silicon enhance grass growth and development, particularly during periods of stress or unfavourable growing conditions. However, little information has been made available regarding the role of silicon in plant function and stress tolerance, so that Greenkeepers can make informed decisions regarding the use of silicon as a component of an integrated turfgrass management programme.


Silicon is one of the most abundant mineral elements found in soils. In fact, only oxygen is more common. However, much of the silicon found in soils is present in insoluble forms like silicon dioxide, or iron and aluminium silicates that are not available for plant uptake. Silicon is most readily absorbed by plants as orthosilicic acid, (H4


SiO4 ), which is


soluble in the soil solution, and forms after weathering of silicon-based minerals or the addition of silicon fertilisers like potassium silicate. Despite its abundance in most soils, silicon deficiencies may occur. Deficiencies are most prevalent in areas with frequent, heavy rainfall and are most common in soils with high levels of organic matter or those with low cation exchange capacity that are easily leached. Quartz


sands, frequently used to construct golf course putting greens and modern sports pitches, generally have a low cation exchange capacity and may develop silicon deficiency over time. Silicon is generally a forgotten element and is usually not considered essential for plant growth because of its ubiquitous presence in soils. Although many plant species are able to grow and develop in the absence of silicon, most plants, including grasses, respond favourably to applications of silicon. Therefore, silicon is currently classified as a beneficial, rather than essential, element for plant growth and development. Beneficial effects of silicon fertilisation have been studied extensively in grasses, and include improved cell wall strength and leaf erectness, increased tolerance to environmental stress, and decreased susceptibility of plants to pests and diseases.


Silicon is transported from the roots to shoots in the xylem along with the transpiration stream, with silicon being deposited in leaf epidermal cells, xylem vessels, cell walls and cuticle following evaporation of


transpiration water. The


accumulation of silicon in


epidermal cells and cell walls results in the development of more erect leaf blades and a thicker, stronger cuticle layer which limits non-stomatal transpiration and water loss. Reduced transpiration and water loss


through the cuticle layer has the potential to minimise water usage, especially during hot, dry conditions. In addition to promoting cleaner and more uniform cutting, enhanced leaf erectness also increases the uniform distribution of light within the turf canopy, which in turn increases potential photosynthetic capacity during periods of stress. Increased traffic tolerance has been observed following silicon applications. University research has demonstrated that deposition of silicon improves wear tolerance by strengthening cell wall polysaccharide and stabilizing lignin formation to limit damage commonly observed in intensively used turf areas. The mechanism by which silicon reduces pathogen infections has been investigated. It is understood that deposition of silicon in the cell walls


creates a physical barrier that


reduces the ability of fungal hyphae to penetrate into leaf tissue. Accumulated orthosilicic acid polymerises into polysilicic acid and then transforms to amorphous silic,


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