Response of biochar induced carbon mineralization priming effects to additional nitrogen in a sandy loam soil

Abstract

The responses of soil carbon (C) mineralization priming effects induced by biochar to nitrogen (N) and the mechanisms in relation to soil microbial community and C availability were examined. A sandy loam soil (under a long-term C3 crop rotation) amended with biochar derived from maize straw (C4 crop) with or without additional N was incubated for 30 days. Primed native soil-derived carbon dioxide emission by biochar was -64.4 and -95.9mgCkg-1 in soils without and with N, respectively; and additional N showed no influence on priming effects (-66.9% and -72.0%) during the whole incubation. Whereas, N increased (p<0.05, n=6) the magnitude of priming effects from -68.3% to -83.5% at the early incubation stage (days 0-11) while N decreased (p<0.05, n=6) that from -64.9% to -38.8% at the late incubation stage (days 11-30). Nitrogen increased microbial biomass (p>0.05, n=6) and the proportion of gram-positive (G+) bacteria (p<0.05, n=6) while N decreased the ratios of gram-negative to G+ bacteria (p>0.05, n=6) and aerobic to anaerobic microbes (p<0.05, n=6) as estimated by phospholipids fatty acids at the beginning of the incubation. The opposite impact, however, occurred on day 11 in biochar-amended soils. On the other hand, N had no influence on native-soil derived dissolved organic carbon throughout the incubation in biochar-amended soils. Therefore, the results indicated that N could affect biochar induced C mineralization priming effects through the change of microbial community, especially the increase of G+ bacteria in the soil tested.