A recent study in Scientific Reports by Saowalak Somboon and colleagues evaluated the system-level impacts of combining rice straw-derived biochar with standard urea fertilizer in tropical flooded paddy fields. Managing nitrogen in flooded rice farming remains an environmental and agricultural challenge globally, as a substantial portion of applied fertilizer is lost to the environment through leaching, ammonia gas release, and nitrous oxide emissions. The researchers evaluated four field treatments: an unfertilized control, chemical fertilizer alone, raw rice straw with chemical fertilizer, and biochar combined with chemical fertilizer.

The application of biochar paired with chemical fertilizer delivered the lowest total nitrogen loss, retaining 67 percent of the applied nitrogen within the agricultural system. In comparison, field plots treated only with chemical fertilizer lost 43 percent of their total nitrogen inputs, while plots treated with raw rice straw and chemical fertilizer lost 38 percent. This improved nitrogen retention in the biochar-treated soil was primarily driven by reductions in ammonium leaching and lower rates of ammonia gas release into the atmosphere.

In terms of crop productivity, the biochar and chemical fertilizer combination produced the highest grain yield, reaching 11,823 kilograms per hectare. This significantly surpassed the yields achieved by chemical fertilizer alone, which produced 6,333 kilograms per hectare, and the raw rice straw combination, which yielded 10,577 kilograms per hectare. Furthermore, the biochar treatment achieved the highest nitrogen agronomic efficiency, producing 50 kilograms of rice grain per kilogram of applied nitrogen, compared to 36 kilograms per kilogram for raw rice straw and 25 kilograms per kilogram for chemical fertilizer alone.

Both organic amendments successfully lowered the nitrogen-gas-related global warming potential compared to chemical fertilizer alone. Chemical fertilizer by itself generated a global warming potential of 247 kilograms of carbon dioxide equivalent per hectare, whereas biochar co-application reduced this figure to 187 kilograms of carbon dioxide equivalent per hectare. Raw rice straw co-application achieved a similar reduction, recording 193 kilograms of carbon dioxide equivalent per hectare.

Overall, converting post-harvest crop residues into biochar rather than incorporating raw straw offers a far more effective strategy for tropical rice cultivation. Biochar co-application enhances soil cation exchange capacity and nutrient availability, driving superior harvest yields while mitigating environmental pollution and greenhouse gas impacts.

Source: Somboon, S., Rossopa, B., Yodda, S., Lawongsa, P., Chidthaisong, A., & Sukitprapanon, T.-S. (2026). Effects of biochar co-application with urea on nitrogen losses, rice yield, and nitrogen agronomic efficiency in rice production system. Scientific Reports, 16(1), Article 67235.