Aged biochar stimulated ammonia-oxidizing archaea and bacteria-derived N2O and NO production in an acidic vegetable soil

Abstract

Both nitrous oxide (N 2 O) and nitric oxide (NO) emissions are typically high in greenhouse-based high N input vegetable soils. Biochar amendment has been widely recommended for mitigating soil N 2 O emissions in agriculture. However, knowledge of the regulatory mechanisms of fresh and aged biochar for both N 2 O and NO production during ammonia oxidation is lacking. Two vegetable soils with different pH values were used in aerobic incubation experiments with 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), 1-octyne and acetylene. The relative importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) to N 2 O and NO production was investigated as influenced by fresh and aged biochar amendments. The results showed that AOA dominated N 2 O production in acidic soil, while AOB dominated N 2 O production in alkaline soil. Aged biochar stimulated both AOA- and AOB-derived N 2 O and NO production by 84.8 and 340%, respectively, in acidic soil but only increased AOA-derived N 2 O and NO production in alkaline soil. Fresh biochar amendment increased AOA- and AOB-derived NO in acidic soil and AOA-derived NO in alkaline soil but had negligible effects on AOA- and AOB-derived N 2 O in both soils. Fresh biochar decreased AOA-amoA but increased AOB-amoA gene abundances in acidic soil, whereas aged biochar increased AOA- and AOB-amoA gene abundances in both soils. These findings improved our understanding of N 2 O and NO production mechanisms under different biochar amendments in alkaline and acidic vegetable soils.