Biochar interacted with organic compounds from digestate in controlling N2O emissions
Yunyun Zheng, Lynette K. Abbott, Nanthi Bolan, Hang‐Wei Hu, Sue Jenkins, Bede S. Mickan
Abstract
Treating biochar with digestate can form a C- and N-enriched biochar fertilizer, but its role in controlling N 2 O emission from soil with different pH is unclear. This study assessed N 2 O emission from rhizosphere soil after growing ryegrass with urea, urea plus biochar, solid digestate, and digestate-incorporated biochar, with and without liming. The abundances of bacteria, fungi, two nitrification genes (bacterial amoA ; archaeal amoA ), and four denitrification genes ( nirK , nirS , nosZ for clade I and nosZII for clade II) were quantified using quantitative PCR. Bacterial community composition was characterized using amplicon sequencing. Solid digestate and urea plus biochar decreased N 2 O emission by 48% and 56%, respectively, relative to urea under non-liming. This corresponded to the increased bacterial abundance and greater increases in N 2 O-consuming ( nosZ and nosZ II ) than N 2 O-producing (archaeal amoA , nirK , nirS ) gene abundances. Digestate-incorporated biochar decreased N 2 O emission by 75% compared to solid digestate, with decreased nirK gene abundance and increased prevalence of the denitrifier Dokdonella . Liming resulted in the lowest N 2 O emissions and highest nosZ II gene abundance among all treatments. This study demonstrated the value of incorporating biochar in digestate in reducing N 2 O emission while enhancing plant nutrition.