Silicon (Si) availability in soil and its function in improving plant stress tolerance
Credit: Michał Słota Ph.D., Content Farmers
KEY FACTS
- Silicon (Si) is one of the most abundant elements in the Earth’s crust, making up 28 percent of the mineral component of soil, by weight.
- Si can compose from 0.1 to 10 percent of plant dry weight.
- Despite its abundance, Si is utilized by plants in small amounts.
- Si is not yet considered an essential plant element, but a high Si concentration in leaf tissues can have beneficial effects, especially in conditions of plant stress.
- Foliar sprays with exogenous silicates are effective as pesticides, while stabilized silicic acid sprays increase growth and yield of crops and decrease biotic and abiotic stresses.
- Si supplementation may counteract negative effects of N overfertilization.
FUNCTION
- Benefits of optimal soil concentrations:
- Reduction of phosphorus leaching and improvement of P availability
- Effect on binding other nutrients to soil particles, improving the availability of certain microelements (copper, manganese, zinc, boron)
- Reduction of the uptake of toxic elements (aluminum, excessive amount of sodium)
- Benefits of Si application in foliar sprays:
- Increase in plant height, stem diameter, root length and root activity
- Improvement of mechanical strength of stems
- Improved photosynthetic efficiency
- Alleviation of leaf evaporation/ transpiration losses
- Improved nutrient uptake and metabolism
- Increased concentrations of antioxidant enzymes
- Enhanced resistance to biotic and abiotic stresses.
AVAILABILITY
- Plants absorb Si in the form of orthosilicic acid Si(OH)4 from soil or nutrient solution.
- Silicates refers to silicon compounds such as CaSiO3, MgSiO3, or K2SiO3.
- Si is transported to the aerial parts of the plant and deposited as amorphous SiO2.
- A healthy soil microbiome increases Si dissolution rate and uptake rate by plants.
- Active Si accumulators include monocots such as rice, wheat and sorghum.
