Does soil aging affect the N₂O mitigation potential of biochar? A combined microcosm and field study

Abstract

The application of biochar as a soil amendment to improve soil fertility has been suggested as a tool to reduce soil-borne CO 2 and non-CO 2 greenhouse gas emissions, especially nitrous oxide (N 2 O). Both laboratory and field trials have demonstrated N 2 O emission reduction by biochar amendment, but the long-term effect (>1 year) has been questioned. Here, we present results of a combined microcosm and field study using a powdered beech wood biochar from slow pyrolysis. The field experiment showed that both CO 2 and N 2 O emissions were still effectively reduced by biochar in the third year after application. However, biochar did not influence the biomass yield of sunflower for biogas production (Helianthus annuus L.). Biochar reduced bulk density and increased soil aeration and thus reduced the water-filled pore space (WFPS) in the field, but was also able to suppress N 2 O emission in the microcosms experiment conducted at constant WFPS. For both experiments, biochar had limited impact on soil mineral nitrogen speciation, but it reduced the accumulation of nitrite in the microcosms. Extraction of soil DNA and quantification of functional marker genes by quantitative polymerase chain reaction showed that biochar did not alter the abundance of nitrogen-transforming bacteria and archaea in both field and microcosm experiments. In contradiction to previous experiments, this study demonstrates the long-term N 2 O emission suppression potential of a wood biochar and thus highlights its overall climate change mitigation potential. While a detailed understanding of the underlying mechanisms requires further research, we provide evidence for a range of biochar-induced changes to the soil environment and their change with time that might explain the often observed N 2 O emission suppression.

Gas entrapment and microbial N2O reduction reduce N2O emissions from a biochar-amended sandy clay loam soil

“…Furthermore, the calculation of cumulative NO 3 − -derived N 2 O emissions showed that soil biochar amendment significantly decreased N 2 O emissions by 54%. These results confirmed what has been shown in several lab and field studies before11646566676869, that biochar amendment can mitigate soil N 2 O emission. In addition to N 2 O emission reduction, Cayuela and colleagues showed that soil biochar amendment substantially decreased the N 2 O/(N 2 O + N 2 ) emission ratio64.…”

Risk Evaluation of Pyrolyzed Biochar from Multiple Wastes

“…Adding rice straw-derived biochar in a paddy soil reduced CH 4 emission under ambient and elevated temperature and CO 2 , attributed to the decreased microbial activity along with the increased CH 4 oxidation activity [188]. Soilborne emissions are predominantly the major sources of N 2 O in the air [32] caused mainly by nitrogen transformation microbes in the soil through nitrification and denitrification. Suppression of N 2 O becomes an important climate change mitigation, varying with biomass source and pyrolysis environment.…”

A scientometric review of biochar research in the past 20 years (1998–2018)

“…Increasing number of studies were conducted in recent years to explore the microbial mechanisms of biocharinduced changes in N 2 O/CH 4 emissions from soil (Hagemann et al 2017;Han et al 2016a;Harter et al 2016;Sun et al 2018;Wang et al 2017c). The development of distinct N 2 O-reducing microbial taxa induced by biochar might lower N 2 O emission (Harter et al 2016).…”