Biochar from various sources at different application rates suppresses nitrification activity and N₂O emissions in soil

Biochar is a soil amendment widely used as a strategy to mitigate greenhouse gas emissions, such as nitrous oxide (N₂O), especially by suppressing nitrification, a crucial first step in N2O formation. The effectiveness of biochar in suppressing nitrification depends on its source and application rate. This research investigated the impacts of biochar application derived from corn stover (BC), rice husk (BR), or sawdust (BS) at rates of 0, 5, 10, and 20 tonnes ha-1 on nitrification activity and N2O flux in soil. We conducted the soil incubation experiment for 14 days using the microcosm incubation method to investigate NH4+-N and NO3--N dynamics, N2O emissions, and nitrification activity. BC20 had the lowest nitrification activity, with approximately 70% of NH4+-N remaining in the soil for 14 days. Biochar application had an inhibitory effect. . More inhibition was observed on day 7 across all treatments (8-77%) compared to day 14, when only the BR20 treatment showed inhibition (69%). Compared to the control, it lowered the potential nitrification activity (PNA) by 48-92% decreasing from 597.12 to between 46.59 and311.17 mg NO3--N kg-1 soil h-1. BC presented the lowest daily N2O emissions, ranging from 581.38 to 1,765.31 µg N2O kg-1 soil day-1. The BC, BR, and BS treatments reduced cumulative N2O emissions by 47%, 43%, and 41%, respectively. The results indicate that biochar types and rates, and their interaction, significantly reduced soil nitrification activity and N2O emissions, with the BC application having stronger positive effects. This research underscores the effectiveness of targeted biochar application in reducing nitrogen losses in tropical agricultural systems.