15 Biochar additions as a catalyst for climate-smart agriculture and a sustainable solution to greenhouse gas emissions.

Abstract The role of biochar application in reducing greenhouse gas (GHG) emissions and refining soil health is a subject of extensive research, yet its effects remain questioned. Two sets of experiments were conducted to determine the effects of two varieties of biochar (natural and industrial) on soil fluxes of CH4, N2O, CO2, H2O, soil moister, soil temperature, and aggregate-associated carbon measured at the Caprine Research and Education Unit, Tuskegee University, AL during 12-week. The first experiment (Exp. 1) was conducted to evaluate the effects of industrial biochar on GHG emissions, while the second experiment (Exp. 2) was conducted to evaluate the effects of utilizing natural biochar on GHG emissions from grazing lands. The objectives of this study were 1) to measure the soil fluxes of CH4, N2O, CO2, H2O, soil moister, and soil temperature throughout the experiments using twelve soil chambers (n = 3) without or with the addition of different levels of both industrial and natural biochar (0, 10%, 20%, and 30%/kg soil) measured using LI-COR LI-7810 and LI-7820 Trace Gas Analyzers. Our preliminary results in Exp. 1 showed that industrial biochar amendment linearly decreased the cumulative CO2 emissions by 6% during the experiment (P ≤ 0.05). Compared to the control treatment, the effects of biochar amendment on CH4 (P = 0.24) and N2O (P = 0.13) emissions were not significantly different across the experimental period. In contrast, industrial biochar tends to reduce GHG emissions when its quantity in the soil increases. In Exp.2, natural biochar amendment significantly decreased (P < 0.001) in the cumulative CH4 and CO2 emissions by 26% and 84 % during the experiment, respectively. Industrial and natural biochar has no apparent effects on decreasing N2O emissions because N2O needs time for nitrogen fermentation by soil bacteria. Neither industrial biochar nor natural biochar addition affected soil temperature, but soil temperature was significantly affected by the interactions among biochar, N fertilizer, and time (all p < 0.05). Our study concluded that biochar has the highest potential for reducing CH4 and N2O gasses while increasing soil temperature by increasing the proportion of carbon stored inside. This provides a unique method for biochar’s contribution to soil carbon sequestration. However, the long-term sustainability of biochar effects on varied soil types remains challenging.