Silicon deficiency

Systematically, silicon deficiency belongs to mineral nutrition disorders caused by insufficient availability of monosilicic acid in the soil solution. Accumulator plants such as rice, reeds, and certain grasses are particularly sensitive to the absence of this element.

The biological role of silicon lies in the deposition of amorphous silicon dioxide in the epidermal cell walls. This creates a physical barrier that fungal hyphae and pests are physically unable to pierce to invade plant tissues.

Lack of silicon leads to impaired synthesis of phytoalexins—specific compounds that plants use to defend against pathogens. Without sufficient silicon, the plant's immune system enters a suppressed state, paving the way for secondary infections.

Diagnosis of the deficiency is difficult, as external signs are often masked by symptoms of macronutrient deficiency or the consequences of fungal infections. A final conclusion regarding the deficiency is made based on agrochemical analysis of soil and plant tissue.

Silicon deficiency mainly affects cereal crops, including rice, wheat, and barley, as well as vegetables such as cucumbers and zucchini. In these plants, the ability to withstand powdery mildew, rice blast, and fusarium wilt is reduced.

Serious damage is caused to stem strength. With a silicon deficiency, plants lodge even under moderate wind or rain, making mechanical harvesting virtually impossible and leading to direct grain yield losses.

Reproductive organs are also damaged. Impaired silicon transport blocks proper ear formation and grain filling, which reduces not only the thousand-grain weight but also the overall quality, increasing shriveled grain.

In vegetable growing, silicon deficiency leads to premature fruit wilting. Silicon helps plants retain moisture, preventing excessive transpiration; therefore, under deficiency, plants suffer faster from physiological drought.

The damage also manifests as reduced stress tolerance. Deficient plants tolerate soil salinity and heavy metal accumulation much worse, as it is silicon that blocks the uptake of toxic compounds by the root system.

The primary sign is increased softness and flaccidity of the leaves. If you run your finger along the leaf edge of a cereal crop (e.g., rice or wheat), with sufficient silicon nutrition, you will feel "roughness," whereas with a deficiency, the leaf edge will be smooth and weak.

Mass development of fungal leaf spots is observed, which progress faster than on healthy parts of the field. Pathogens easily overcome weak cell walls, causing necroses that are often confused with common diseases without considering the underlying cause.

Visually, plants may appear lighter in color due to impaired photosynthesis. Silicon improves leaf orientation toward light, and when deficient, plants lose their "architecture," leaves droop, and solar energy absorption efficiency decreases.

• Stem lodging in the absence of severe winds.
• Rapid spread of powdery mildew across the entire crop area.
• Accelerated wilting during midday hours despite adequate soil moisture.
• Impaired grain filling and fruit formation.

Stunted root development is another sign. Silicon promotes root hair growth, so with its deficiency, roots explore the soil profile poorly, making the plant dependent on the topsoil layer.

The primary control measure is the application of silicon-containing fertilizers to the soil. The use of amorphous silicon dioxide, calcium silicates, or industrial slags allows for the restoration of the element's balance in the root zone and ensures long-term protection.

The use of foliar feeds based on soluble silicon is an effective "quick" method. Such treatments create a microscopic protective layer on the leaf surface, preventing the penetration of pathogen spores.

It is important to consider soil acidity. In acidic soils, silicon is less available to plants; therefore, liming or applying dolomite flour indirectly improves the uptake of this element by facilitating the transition of silicates into an available form.

Crop rotation allows for the accumulation of organic residues containing silicon. Including accumulator crops in the rotation that return silicon to the soil after decomposition is an important agronomic practice in organic farming.

Monitoring available silicon in the soil through specialized laboratories allows for the proactive planning of fertilizer applications. Prevention is always more profitable than treating the consequences of epiphytotics caused by weakened crop immunity.