Karnataka Farmers Get Low-Cost Biochar Technology to Revive Depleted Soils

Researchers at the University of Agricultural Sciences - Bangalore (UAS-B) are training farmers in Karnataka to produce biochar from crop residue using a simple, portable drum technology. The initiative, funded under the central government's Rashtriya Krishi Vikas Yojana (RKVY), aims to improve soil health in regions where organic carbon levels have fallen sharply.

Biochar is a charcoal-like substance made by heating organic biomass—such as agricultural waste or wood—in a low-oxygen environment, a process called pyrolysis. The university's technology uses a 200-litre drum with small holes and a pipe that acts as a chimney. Farmers can fill the drum with crop residue like coconut shells, sunflower heads, or mulberry prunings, light a fire using dry grass, and close the lid to restrict air entry. In two to three hours, the residue turns into biochar.

According to Krishna Murthy of the Department of Science and Agriculture Chemistry, UAS-B, the idea was developed with small and marginal farmers in mind. The drums are provided free of cost, and farmers receive training on production and application. So far, 10 farmers each in Chitradurga, Tumakuru, Bengaluru Rural, Kolar, Chickballapur, Ramanagara, Mandya, Mysuru, Chamarajanagar, and Hassan districts have been selected. These progressive farmers were identified by Krishi Vigyan Kendras in each district.

The biochar preserves organic carbon that would otherwise be lost as carbon dioxide during open burning. Pyrolysis locks 50% to 80% of the carbon into a stable form that resists decomposition for years, directly rebuilding Soil Organic Carbon (SOC) stocks depleted by intensive cropping. Field trials indicate biochar can improve crop productivity by 10% to 30% and water-holding capacity by 10% to 25%, with the greatest benefits in soils with low SOC.

Karnataka faces a serious soil health crisis. The Bhoochetana initiative in 2009 found 52% of sampled fields deficient in SOC, and a 2017-2024 state analysis confirmed that more than half the state's farmland falls below the critical 0.5% SOC threshold. Kolar district is the worst affected, with over 94% of its farmland in the low-SOC category. Black soil tracts in North Karnataka—Belagavi, Vijayapura, Kalaburagi, Bidar, Yadgir, and Bagalkot—are similarly depleted due to continuous cotton and oilseed cultivation. Coastal districts retain relatively healthier SOC levels.

The UAS-B researchers have tested the technology on their own fields and obtained positive results in increasing soil fertility. By equipping farmers with this low-cost method, the university hopes to reverse the decline in soil health and boost agricultural sustainability across the state.