Silicon (Si)

Mark Howiesonin Consultancy

Silicon.jpgInterest 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, (H4SiO4), 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, which forms a thickened Si-cellulose membrane. By this means, a double cuticular layer is formed, which protects and mechanically strengthens the grass plant. In addition, it is believed that silicon applications stimulate and enhance the defence mechanisms of plants to limit disease severity.

Applications of silicon-based products induce mechanical and biochemical changes in plant growth and development that may reduce water use, promote more erect leaf growth and increase resistance to pests and disease. One such product is Salute™ WSP® is a unique, dry blend of natural humic substances, seaweed extract, potassium silicate, plant saponins, carbohydrates, sucrose, amino acids and beneficial bacteria in pre-measured water soluble packets.

By incorporating silicon-containing products into an integrated management programme, plants can be conditioned to increase stress tolerance and limit susceptibility to pathogens. Additional benefits of silicon fertilisation may include increased wear tolerance, enhanced ball roll and more uniform cutting of turfgrass.

Silicon-containing products represent a valuable tool for improving plant growth and development during periods of stress and unfavourable growing conditions, and should be considered valuable components of integrated management programmes.
Benefits of using Potassium silicate in turf are:

• Silicon in plants helps strengthen cell wall tissues and is found in epidermal cells
• In grasses, silicon appears in intracellular bodies such as silica cells or bulliform cells of the epidermis of leaf surfaces, located along the midrib of the blades
• Reduced water loss during periods of dry weather
• Increases ball roll and green speed
• Improves uniform cutting and appearance of turf, especially in stadia situations
• Silicon helps lift the leaf blade to allow a cleaner cut with dwarf perennial rye species
• Can be used as part of an integrated programme to help prevent leaf spot by hardening of the cell walls
• Assists in removal of Annual Meadow-grass seed heads
• During seeding, an application of silicon lifts the seed head, allowing better collection by regular mowing or verti-cutting
• Allows better cutting of uneven spring growth due to the presence of different turf grass species

Contact Sherriff Amenity on 01638 721888 for information regarding Summer Stress Relief Programmes.

Becker Underwood is one of the world's leading suppliers of speciality products to the turf industry and is renowned worldwide for its high focus on research and development.

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