A sandy-loam soil-column experiment examined urea with 1–4% corncob biochar by weight. Biochar changed pH, cation-exchange capacity, and water retention. The 3% rate maximized ammonium stabilization in subsoil, whereas 4% produced the highest soil-profile nitrate concentration and increased nitrate leaching, showing that more biochar was not automatically better.
Key findings
- Biochar significantly altered soil properties. The 3% rate most strongly stabilized NH4+ in subsoil, associated with improved CEC. The 4% rate produced the highest soil-profile NO3− concentration but also increased nitrate leaching, indicating divergent ammonium and nitrate mechanisms.
Why this matters globally
Nitrogen loss from coarse soils reduces fertilizer efficiency and threatens groundwater. The study cautions that biochar guidance must be tailored to soil, feedstock, and fertilizer conditions rather than using a universal application rate.
Thai researcher contribution
Naresuan University and Chiang Mai University contributed depth-resolved evidence directly relevant to fertilizer management and agricultural-residue valorization in Thailand.
Limitations to consider
This greenhouse column study used one soil, one corncob biochar, and a limited duration. It did not reproduce field rainfall, roots, multiseason microbial dynamics, or crop yield. Weight-based rates may be high and require field-scale conversion and economic assessment.