Biochar mitigated more N₂O emissions from soils with the same origin ecosystem as its feedstocks: implications for application of biochar

Agroforestry biowaste compiles large amount of solid waste, which could be pyrolyzed into biochar and applied as soil amendment. The application of biochar has emerged as an excellent tool to mitigated the greenhouse gases emissions. However, effects of biochar could be varied according to soil type, feedstock type and rate of biochar application.

We studied the effect of three types of biochar (FS, fruit shell of Camellia oleifera-based; MS, spent mushroom substrate-based and RS, rice straw-based) on N₂O emissions with nitrogen treatment N (urea, 0 and 0.02%) from and two soils with different origin (rice paddy soil, RPS and C. oleifera plantation soil, CPS).

FS and MS biochar significantly reduced N₂O emissions in fertilized CPS by 66% and 33%, respectively, while that in RPS were increased by 74% and 49%, respectively. After RS biochar addition, N₂O emissions were decreased by 82% only in fertilized CPS, indicating that FS and MS biochar applied in soil with the same origin as those of biochar feedstocks efficiently mitigated N₂O emission rates. The relatively lower soil pH in CPS increased profoundly relative to RPS after biochar was added which contributed substantially to N₂O emissions reduction, that result could be supported by the increased abundance of nosZ in RPS with nitrogen and biochar. Simultaneously, the higher soluble C and N of MS and FS biochar could increase that of RPS after application, which could further enhance N₂O emissions in RPS.

Biochar mitigated more N₂O in soils with the same origin as that of biochar feedstocks compared with that of different origin ecosystems. Mitigating N₂O emissions should consider the origin ecosystem of both biochar feedstock and soils, both of which profoundly impact the outcome of soil N₂O mitigations.