Silicon

Silicon deposited beneath the leaf and stem cuticle and within cell walls forms a rigid, glass-like layer that mechanically reinforces plant tissue. This is linked to improved standability and reduced lodging in tall or heavily laden cereals, and to a physical barrier that can make leaf tissue more difficult for chewing and piercing-sucking pests to penetrate.

In several silicon-accumulating species, adequate silicon supply has also been associated with reduced severity of some fungal diseases, and with improved tolerance of certain abiotic stresses, though the strength of these effects varies by species and growing conditions.

Plant-available silicon exists in soil solution as silicic acid, which is distinct from the abundant but largely insoluble silica in quartz sand. Availability depends on soil weathering stage, mineralogy, pH, and organic matter, and is generally lower in highly weathered, leached tropical soils despite their often sandy, silica-rich texture.

• Highly weathered or intensively leached soils often have lower plant-available silicon
• Repeated harvesting and removal of silicon-rich straw or residue can deplete soil silicon over time
• Returning rice straw and similar residues to the field helps recycle silicon back into the soil

Rice and sugarcane are classic silicon accumulators, and both are the crops with the most consistent, well-documented responses to silicon supply, including reduced lodging and, in rice, improved resistance to some fungal diseases and certain insect pests. Wheat, also a member of the grass family, shows a more moderate response.

Non-grass (dicot) crops generally take up and accumulate far less silicon and show smaller, less consistent benefits, so silicon management is a more established practice in grass crops than across agriculture broadly.

Silicon has been reported to help alleviate manganese and iron toxicity in some waterlogged or strongly reduced soils, a situation relevant to lowland rice. It is not a substitute for balanced nitrogen, phosphorus, and potassium fertility, but can complement it in silicon-responsive crops.

Because responses to silicon vary considerably by species, soil, and growing system, silicon management is best regarded as a complementary practice for responsive grass crops rather than a universal input. Evidence for benefits is strongest in flooded rice and sugarcane systems.