Can silicon crop sprays benefit growers this season?
© Tim Scrivener Despite silicon being the world’s second most abundant element, making up 25% of the earth’s crust, crops can still benefit from its application, which has a vital role in plant development by strengthening crops, optimising yields and reducing the risk of pest and disease attacks.
That’s because while there are copious amounts of silicon, it can only be utilised by plants when it is present in a bioavailable form known as monosilicic acid.
Growers, agronomists and crop production specialists are now starting to see the benefits of optimising silicon nutrition as a means of sustainably promoting yields and reducing reliance on artificial inputs.
With nutritional products emerging in the marketplace, we take a closer look at the role the element plays in crop production and how additional silicon applications could benefit growers this season.
See also: What milling premium do growers need to cover extra N costs?
Functions of silicon relating to plant growth
- Soil conditioner: Long-chain silicon polymers that are not bioactive, help bind soil particles to reduce leaching and increase aeration
- Bioregulation: Bioactive silicon in the form of monosilicic acid helps with plant growth and mitigates stresses
- Structural component: Bioactive silicon then accumulates within plants, increasing the strength and resilience of cell walls
How does silicon benefit crops?
Avice Hall, crop researcher at the University of Hertfordshire, says that silicon nutrition has been neglected over the years and there is considerable opportunity to enhance crop development through its accurate use.
“Silicon is required by all plants, and has a role in increasing chlorophyll levels, with potential to optimise yields, as well as providing resistance against pest and disease attack,” says Dr Hall.
Despite this, silicon is not classed as an essential crop element, most probably because it has no clear deficiency symptoms, she notes.
Once absorbed by the plant, the element accumulates within and between cells. All plant hairs (known as trichomes) contain silicon, but the amount that is deposited in the plant (after treatment with silicon) greatly exceeds what is found in the hairs.
Silicon strengthens the cell walls and increases leaf cuticle thickness, allowing plants to create a tough outer coating with extra leaf hairs. This makes it more challenging for fungal hyphae to penetrate the crop, and restricts the ability for pests to feed on crops.
Benefits of silicon
- Increased number and length of leaf hairs
- Strengthens cell walls and increases leaf cuticle thickness
- Increases ability to withstand disease and pest attack
- Improves resistance to abiotic stress
- Potential to lift yield and growth rate
- Reduces risk of lodging and wilting
Stronger defence
With enhanced natural defence capabilities and strengthened plant structure, plants are better able to withstand stress and tolerate more extreme weather conditions.
They are also less prone to wilting and lodging and enables crops to enhance energy use to promote growth rates and yield.
“Plants have two defence pathways,” continues Dr Hall.
The first is the passive defence pathway that occurs in all plants and is effectively enhanced by silicon in the plant.
The other defence pathway is known as the active defence, which usually becomes effective as or after pathogen infection. This is mediated through effector and R genes.
“Passive defence provides resilience against virtually all pests and disease, through morphological traits such as wax and cuticle thickness, cell wall thickness and leaf hairs.
“Silicon nutrition enhances the passive defence pathway, resulting in pest and disease reduction by 40-50%.”
Furthermore, silicon encourages crops to absorb beneficial elements such as zinc, calcium and nitrogen.
It can also help to regulate phosphorus uptake and prevent toxicity from trace metals present in soils.
Two silicon products available for growers
Orion
One pioneering firm in silicon-based biostimulant technology is British crop nutrition specialist, Orion.
Established in 2005, the company has grown significantly over the past 15 years to offer a range of silicon products that can be used on a wide range of crops.
Trial work reveals promising results in reducing damage from cabbage stem flea beetle in oilseed rape, slug damage in wheat seedlings and enhanced efficacy of existing crop chemistry.
James Kennedy, Orion’s managing director, explains how the company’s unique iNHiB technology delivers bioactive, plant-available silicon directly to the crop to deter pest and pathogen attack.
“With input prices rising and a reduction in the number of chemicals available, silicon represents a new way to improve plant health and increase crop yields,” says Mr Kennedy.
One of their products, known as Sirius, contains 21% silicon and is registered for use in field crops, the fruit industry, ornamentals and ferigation lines.
For field crops, applications can be used as part of a regular programme tank mixed with traditional fungicide timings in the spring at a rate of 0.25-0.5 litres/ha.
Repeat application are best to allow accumulation in areas of new growth, with four being the maximum number of applications made to a crop.
Flea beetle
In a cabbage stem flea beetle trial, a 0.5 litre/ha spray provided up to 60% reduction in pest damage, just one day after application, explains technical manager Kate Williams.
One spray provided up to two weeks of protection, defending oilseed rape when it was most vulnerable to pest attack.
The trial also investigated the combined use of Sirius with the pyrethroid lambda, which was found to strengthen pesticide efficacy, so much so that rates could be reduced and efficacy maintained.
“We believe Sirius provides a synergist effect, which helps the pesticide to be more active against the pest for a more effective kill,” she says.
“However, silicon is not a guaranteed silver bullet for solving cabbage stem flea beetle issues. But what it will do is protect the crop before the pest has arrived, reduce damage in early infection stages and make sprays more effective.”
The silicon-based product has also proved effective in aphid control, reducing numbers of pests on each plant, feeding times and, consequently, growth rates.
Levity Crop Science
Another silicon biostimulant set to benefit farmers is a foliar spray from Levity Crop Science, called Zeme.
Containing 21% silicon, the product helps to transport and distribute silicon evenly throughout the plant to improve the health and vigour of crops.
Like many trace elements, silicon is not phloem mobile, and so is transported through the xylem, explains the firm’s managing director, David Marks.
However, some crops are more efficient than others and can be broadly classified into groups according to how well they take up silicon from soils.
“Rice, sugar cane and other wetland cereal crops are strong accumulators and can contain in excess of 15% silicon.
“Wheat, barley and other dryland grass species are intermediate accumulators and contain 1-3% silicon. Tomatoes, potatoes and other dicots are weak accumulators and contain less than 0.5% silicon,” he says.
Stronger leaf
Once in the leaf, silicon develops into silica gel known as opals, which strengthen the leaf for an added layer of defence and reduce water loss. However, once in this form, silicon can no longer be redistributed.
Mr Marks says Levity’s specialist Si-X technology improves the distribution of silicon and provides strength to the crop by stimulating the influx and efflux of silicon into and out of the xylem.
It also delays the formation of opals, and triggers a stronger metabolic anti-stress response in crops.
Applied at 1 litre/ha three to four times throughout the growing season, the product can improve grain development, stem thickness and height, and produces a stronger, more upright crop.
Furthermore, the company claims its silicon products have the potential to improve post-harvest shelf life in leafy fruit and veg.
