Silicon for crops: how a common mineral makes plants tougher
Silicon is everywhere in soil, yet crops can run short of the form they can use. A review co-authored by Dr. Abhishek Mathur brings together research on how silicon helps crops cope with drought, salt, disease and pests. Here is what it says, which crops gain most, and where the evidence stops.
Key points
- Silicon is the second most common element in the earth's crust, but roots can take it up only in a dissolved form. Years of cropping, especially rice and sugarcane, can run that form down.
- It is not officially an essential plant nutrient, but it is a beneficial one. Its benefits show most when crops are under stress.
- Inside the plant it forms glassy deposits in and between cells, which help against drought, salt and toxic metals, and make leaves harder for fungi and sucking pests.
- Rice, wheat, sugarcane, maize and other grasses take up the most. Some crops, such as tomato, take up very little.
- What to do: return rice straw and husk to the soil instead of burning them, and ask your KVK whether your soil and crop need a silicon fertilizer.
What silicon is, and how plants take it up
Silicon (Si) is an element; silica is its compound with oxygen (silicon dioxide), the main part of sand and quartz. Soil holds huge amounts of it, but mostly locked in minerals that roots cannot absorb. Plants take silicon up only as silicic acid, a form dissolved in soil water. It travels up with the water to the leaves and stems, where it is laid down as tiny glassy bodies called phytoliths.
Scientists have not shown that crops need silicon to complete their life cycle, so it is not classed as an essential nutrient. It is called a beneficial element: one that helps many crops, especially when they are under stress. Crops that take up a lot of it, such as rice and sugarcane, remove it from the field with every harvest, so long-term cropping can leave less of the usable form in the soil.
The review was published in 2021 in Plant Archives. Its authors are Manjit Kaur and Sanjeev Kalia of RIMT University, Punjab; Subodh Kumar Bhatnagar of the Society for Plant Research; Tarun Kumar of MB PG College, Haldwani; and Dr. Abhishek Mathur, then with the Society for Plant Research and the R&D department of NCS Green Earth, Nagpur. Dr. Mathur was the fifth author.
Which crops gain most
Crops differ a lot in how much silicon they take up. Grasses and cereals pull it in actively through their roots; many broad-leaved crops take up less, and a few keep it out.
| Group | Examples | What it means |
|---|---|---|
| Cereals and grasses | Rice, wheat, barley, maize, sugarcane | Take up the most; most likely to respond |
| Some broad-leaved crops | Cucumber, sunflower, ash gourd | Also take it up actively; can respond |
| Crops that keep it out | Tomato, faba bean | Take up little; benefit less certain |
How silicon helps crops under stress
- Drought. Silica in the leaves cuts water loss and keeps leaves upright. Studies cited in the review found better water status in silicon-fed wheat and sorghum.
- Salty soil. Silicon can limit how much sodium reaches the leaves. The review cites studies in barley and tomato seedlings.
- Toxic metals and acid soils. Silicon fertilizers are slightly alkaline, and silicon can reduce damage from excess manganese, iron, aluminium and cadmium.
- Cold and strong sunlight. Studies on wheat, soybean and sugarcane found less damage from freezing and from ultraviolet light.
- Nutrients. Some studies found better uptake of potassium and phosphorus when silicon was supplied.
Silicon against diseases and pests
Silicon works in two ways against disease. It builds a physical barrier in the leaf that fungi find harder to break through, and it helps the plant switch on its own defences, such as protective compounds made at the site of infection. In rice, silicon has been linked with less blast, brown spot, sheath blight and other diseases. One study cited in the review reports these results with calcium silicate, a common silicon fertilizer:
Against pests, harder tissues are tougher to feed on. The review cites less feeding and breeding by the white-backed planthopper in rice, by aphids in potato and wheat, and by whitefly in cucumber, and harder sugarcane stems that resist shoot borer. Silicon has also been reported to reduce powdery mildew and root rot in cucumber.
In simple words: silicon makes the plant's "skin" tougher and helps it defend itself. It works best as a steady support, especially for rice, wheat and sugarcane, not as a quick cure.
What this review does not tell us
- It is a review: it summarises other researchers' studies. The authors did not run new experiments.
- Many of the studies were done in pots, in nutrient solutions or in other countries. Results in Indian fields can differ.
- It gives no dose, timing or cost for Indian soils and crops, and does not compare silicon sources or test any product.
- As the review itself notes, silicon's benefits are clearest under stress. In a healthy crop on soil with enough usable silicon, the gain may be small.
- Crops that take up little silicon, such as tomato, may gain less.
Indian soil scientists have also argued that silicon deserves more attention in tropical soils, especially for rice and sugarcane (Meena and colleagues, 2014). The best next step is field trials on Indian soils that measure yield and cost.
What you can do
- Recycle silica-rich residues. Rice straw and husk hold a lot of silica. Compost them or work them into the soil instead of burning, so the silicon and other nutrients go back to the field.
- Know your crop. Rice, sugarcane, wheat and maize respond most. If you have grown them on the same land for many years, ask whether your soil is low in usable silicon.
- Ask before you buy. Silicon fertilizers include calcium silicate, potassium silicate and products made from rice-husk ash. Ask your KVK or soil-testing lab whether your soil and crop are likely to respond, buy from a licensed dealer, and follow the label.
- Use it as support, not as a cure. Silicon does not replace balanced NPK, good seed or proper disease and pest control. It helps the crop cope; it will not stop an outbreak on its own.
What it means
For crops like rice and sugarcane, silicon is a low-risk way to help plants handle stress, and recycling straw is the cheapest place to start. Dr. Mathur's wider work on mineral and microbial inputs builds on findings like these.
NanoKheti's Fertiliser Activator contains precipitated silica as a carrier. It is not sold as a silicon fertilizer, and it was not part of this review.
