Can Biochar Improve Soil? What Farmers Should Know Before Adding It to Their Fields

Farm residues that are often treated as waste can be converted into biochar, a carbon-rich material used as a soil amendment. ICAR-CIRCOT discussed cotton-stalk biochar on September 18, including ways to improve its nutrient value and create possible economic opportunities for farmers.

Biochar is produced by heating biomass under limited oxygen rather than allowing it to burn completely. Crop residues, wood and other plant materials can be used as feedstock. Its properties depend on the original material and the conditions used during production.

Biochar is different from ordinary ash. It retains much of the carbon from the original biomass and can have properties that affect soil structure, nutrient retention and water availability. Research also shows that its performance can vary with soil type, feedstock and application rate.

Cotton cultivation produces large quantities of stalk residue after harvest. ICAR-CIRCOT is examining whether this material can be converted into biochar instead of being treated only as agricultural waste. The institute has also highlighted the logistical challenge of transporting bulky cotton stalks.

ICAR-CIRCOT scientists are also studying enriched biochar made using banana pseudostem sap and phosphate-solubilising bacteria. The research aims to improve the soil-nutrient value of biochar rather than treating every type of biochar as identical.

Can biochar improve soil?

Research has linked biochar with changes in soil physical, chemical and biological properties. These can include improved water-holding capacity, nutrient retention, soil structure and microbial activity. The effects are not uniform, and results depend on the biochar used and the characteristics of the soil.

A recent research project involving ICAR-Indian Institute of Soil Science, Bhopal, is examining biochar’s effects on soil properties and crop performance. The research includes different biochar sources and their application in agricultural soils, showing why farmers need evidence specific to their crops and conditions.

Biochar should not be treated as a direct replacement for fertiliser. Research suggests it can influence nutrient availability and retention, but the result depends on soil conditions, biochar characteristics and how it is combined with other inputs.

An ICAR review notes that biochar can improve nutrient availability and reduce nutrient losses in some systems. Farmers should therefore view it as a soil amendment that may complement nutrient management rather than replacing fertilisers automatically.

Biochar can influence the water-holding characteristics of soil. This is one reason researchers are studying it for soils with low organic matter or limited water availability.

The response depends on soil texture, biochar properties and application rate. Farmers should not assume that adding more biochar will always improve moisture retention. Local trials can help identify suitable application levels.

Does every biochar work the same way?

No. Feedstock and production conditions can change the properties of biochar. Cotton stalks, rice residues, wood and other materials can produce chars with different characteristics.

Temperature during production also matters. An ICAR technology note says its biochar production system can generate char with different properties by changing processing conditions, including carbon content and pH.

There is no single application rate suitable for every farm. The right amount depends on soil properties, crop, biochar source and how the material was produced.

Research on okra and brinjal at ICAR-IISS tested different biochar sources and rates, both alone and with farmyard manure and recommended fertiliser doses. Such trials show why farmers should follow crop-specific recommendations instead of using arbitrary quantities.

Small-scale production is possible with suitable technology, but farmers should not simply burn crop residues in open fields and call the resulting material biochar. Controlled production is needed to obtain consistent material and manage smoke, heat and other emissions.

ICAR-CIAE has developed an annular-core biochar production system with adjustable processing conditions. The technology can be customised for different biomass types and reactor capacities.

What about cotton stalk transport?

Transport can become a major cost because crop residues are bulky compared with their usable processed material. ICAR-CIRCOT has specifically highlighted this issue while discussing cotton-stalk biochar.

The institute has suggested decentralised conversion systems as one way to reduce the need to transport large quantities of raw stalks over long distances. Biochar could create value from crop residues that otherwise have limited economic use. ICAR-CIRCOT is also exploring whether cotton-stalk biochar can connect with carbon-credit systems.

The institute discussed collaboration on carbon-credit certification, with the stated aim of creating possible financial benefits for farmers while promoting residue management and carbon storage. Farmers should not assume that producing biochar automatically generates a payment. Carbon-credit projects require measurement, documentation, verification and certification under the rules of the relevant programme.

ICAR’s recent discussion focused on exploring a framework for certification and farmer benefits. This means the opportunity is being developed and should not be treated as guaranteed income for every farmer using biochar. Farmers should first identify the feedstock used to make the biochar and understand how it was produced. They should also check its pH, nutrient properties and other relevant characteristics before applying it to soil.

A soil test can help determine existing nutrient and acidity conditions. Farmers should then seek recommendations from agricultural scientists or their local KVK before applying large quantities.

Can biochar replace compost?

No. Biochar and compost are different materials with different properties. Compost supplies organic matter and nutrients through decomposed biological material, while biochar is a carbon-rich product created through controlled thermal processing. Research has also examined biochar together with farmyard manure and recommended fertilisers. This suggests that combining materials may be useful in some systems rather than treating biochar as a complete replacement.

For farmers growing cotton and other crops, biochar offers one possible route for turning residues into a useful soil amendment. But its value depends on production quality, transport costs, soil conditions and the crop being grown. ICAR’s current work shows that researchers are moving beyond residue disposal and examining nutrient-enriched biochar, decentralised production and possible carbon-credit models.

The practical question for farmers is not simply whether biochar is good for soil. It is whether a particular biochar, produced from a known feedstock and applied at a tested rate, suits their soil and crop. Farmers should therefore begin with soil testing and local technical advice. If cotton stalks or other residues are available, they can also compare the cost of converting them into biochar with the cost of other residue-management options before investing in equipment.