Unweathered Wood Biochar Impact on Nitrous Oxide Emissions from a Bovine‐Urine‐Amended Pasture Soil

Abstract

Low‐temperature pyrolysis of biomass produces a product known as biochar The incorporation of this material into the soil has been advocated as a C sequestration method. Biochar also has the potential to influence the soil N cycle by altering nitrification rates and by adsorbing or NH3 Biochar can be incorporated into the soil during renovation of intensively managed pasture soils. These managed pastures are a significant source of N2O, a greenhouse gas, produced in ruminant urine patches. We hypothesized that biochar effects on the N cycle could reduce the soil inorganic‐N pool available for N2O‐producing mechanisms. A laboratory study was performed to examine the effect of biochar incorporation into soil (20 Mg ha−1) on N2O‐N and NH3–N fluxes, and inorganic‐N transformations, following the application of bovine urine (760 kg N ha−1). Treatments included controls (soil only and soil plus biochar), and two urine treatments (soil plus urine and soil plus biochar plus urine). Fluxes of N2O from the biochar plus urine treatment were generally higher than from urine alone during the first 30 d, but after 50 d there was no significant difference (P = 0.11) in terms of cumulative N2O‐N emitted as a percentage of the urine N applied during the 53‐d period; however, NH3–N fluxes were enhanced by approximately 3% of the N applied in the biochar plus urine treatment compared with the urine‐only treatment after 17 d. Soil inorganic‐N pools differed between treatments, with higher concentrations in the presence of biochar, indicative of lower rates of nitrification. The inorganic‐N pool available for N2O‐producing mechanisms was not reduced, however, by adding biochar.

Mitigating Global Warming Potentials of Methane and Nitrous Oxide Gases from Rice Paddies under different irrigation regimes

“…Wang et al (2012) reported that biochar application decreased N 2 O emissions up to 54 and 53 % during rice and wheat seasons. However, Clough et al (2010) and Kristiina et al (2011) found that biochar application had no effect on N 2 O emissions. Zhang et al (2012) reported that biochar amendment (20 t ha -1 ) in a Chinese paddy soil increased GWP by 39 % in the first growing cycle; however, the overall GWP decreased (7-18 %) in the second consecutive growing season.…”

A Review of Biochar and Soil Nitrogen Dynamics

“…To date, several studies have shown that the addition of biochar to soils can mitigate N 2 O emissions in situ from soybean and grass ecosystems [48], following ruminant urine deposition [49], in wheat plots [50] and during laboratory or greenhouse incubations under various conditions [8,9,47,[51][52][53][54][55][56][57][58][59][60][61] while other studies have found no differences or even increases in cumulative N 2 O emissions after biochar addition [61][62][63].…”

Biochar Impacts Soil Microbial Community Composition and Nitrogen Cycling in an Acidic Soil Planted with Rape

“…Some has shown no effect 13 and some that biochar increased soil N 2 O emissions. 14 In addition to the uncertain effect of biochar on N 2 O emission, the factors and mechanisms of the influence of biochar on N 2 O remain unclear due to the complex N 2 O formation pathways. N 2 O can be produced from several closely related biological processes in soil, including nitrification, nitrifier denitrification, denitrification, codenitrification, dissimilatory nitrate reduction to ammonia, nitrate assimilation, and chemodenitrification, among which nitrification and denitrification are predominant.…”