Influence of bioenergy crop Jatropha curcas amendment on soil biogeochemistry in a tropical vertisol: Fid-Bau Portal

Influence of bioenergy crop Jatropha curcas amendment on soil biogeochemistry in a tropical vertisol

Kollah, Bharati / Dubey, Garima / Dunfield, Peter / Mohanty, Santosh Ranjan

Abstract Experiments were carried out to determine how the incorporation of biomass from the bioenergy crop Jatropha curcas into a tropical vertisol affects the biogeochemical processes important for greenhouse gas (GHG) fluxes, specifically methane ($ CH_{4} $) production, carbon dioxide ($ CO_{2} $) production, and $ CH_{4} $ consumption. Leaf biomass of J. curcas was incorporated at 0.1, 0.5, and 1 % (w/w) into soil maintained under 60 % of moisture-holding capacity (MHC). Biomass addition significantly stimulated potential $ CH_{4} $ and $ CO_{2} $ production while inhibiting potential $ CH_{4} $ consumption. When 1 % of J. curcas biomass was added to soil, potential $ CH_{4} $ production increased nearly 50-fold over 60 days, from 2.45 μg $ CH_{4} $ $ g^{−1} $ soil $ day^{−1} $ in unamended soil to 115 μg $ g^{−1} $ $ day^{−1} $ in soil containing leaf biomass. Soil $ CO_{2} $ production also doubled when the J. curcas biomass was added. The potential $ CH_{4} $ consumption rate of soil was inhibited almost completely by 1 % of added biomass. The culturable methanotroph population was positively correlated with the $ CH_{4} $ consumption rate (r = 0.961, p < 0.0001) and was inhibited 20-fold by 1 % of biomass addition. In contrast, the total population of aerobic heterotrophs culturable on a complex medium increased from 11 to 59 × $ 10^{6} $ of colony-forming units (CFU) $ g^{−1} $ of soil after biomass addition. Significant positive correlation was observed between the total heterotroph population and both $ CH_{4} $ production (r = 0.861, p = 0.0003) and $ CO_{2} $ production (r = 0.863, p = 0.0002). Our study shows that biomass from the bioenergy crop J. curcas can affect soil biogeochemical processes that control GHG emissions. We propose that a high incorporation of J. curcas biomass could dramatically change the $ CH_{4} $ flux in tropical soil by simultaneously increasing $ CH_{4} $ production and decreasing $ CH_{4} $ consumption, and we therefore recommend that biomass incorporation to soil be minimized (<0.1 %) as a strategy to mitigate GHG emission.