How do biochar size fractions and organic fertilizers interactively influence nitrous oxide emission from a tropical vertisol?

Abstract

Background: Nitrous oxide (N 2 O) emission from agriculture is increasing alarmingly due to intensive application of inorganic and organic fertilizers. Recently, biochar has been identified as a promising additive to improve agriculture by enhancing soil function and mitigate greenhouse gas emission. However, it is unclear how biochar of different size fractions influences N 2 O emission from agricultural soil. Aims:The current experiment aims to understand how the size of biochar (BC) and organic fertilizers interactively influence N 2 O emission from a tropical vertisol.Methods: BC was prepared using pigeon pea (Cajanus cajan) stalks and further processed to obtain two size fractions (<0.25 mm or 0.25-2.00 mm). Organic fertilizers (vermicompost [VC], poultry manure [PM], or farmyard manure [FYM]) and BC were added to soil to evaluate N 2 O emission potential. BC was added to soil at 10% (w/w), whereas the organic fertilizers were added at 80 kg N ha -1 . Emission of CO 2 and the abundance of 16S rRNA and amoA gene copies were estimated after incubation period. The interactive effect of BC size fractions and organic fertilizers were statistically evaluated.Results: Both BC and organic fertilizers stimulated N 2 O emission in soil. BC of larger size stimulated N 2 O emission (µg N 2 O produced g -1 soil day -1 ) more than smaller size.Of the three organic fertilizers, PM resulted highest N 2 O (0.380) emission followed by FYM (0.240) and VC (0.210). BC (0.25 mm) + PM produced least N 2 O. Abundance of heterotrophic bacterial 16S rRNA gene copies and ammonia-oxidizing bacterial (AOB) amoA gene copies were highest in PM + BC and lowest in control. Significant relation (p < 0.0001) existed among N 2 O emission, CO 2 emission, and microbial abundance.Conclusions: BC of small size fraction along with organic fertilizers can be an effective strategy to mitigate N 2 O emission from tropical vertisol.

Soil science challenges—An interdisciplinary overview of current and future topics

“…In this issue, Kollah et al. (2022) report enhanced N 2 O emissions with fertilizer application when larger biochar particles (0.25–2.00 mm) were applied in tropical vertisols, but organic fertilizer together with smaller biochar particles (< 0.25 mm) reduced the emissions. Furthermore, certain plants were found to produce polyphenols that inhibit nitrification and thus the risk of denitrification and subsequent N 2 O emissions as presented by Girardi et al.…”

Biochar use in agriculture as a nature-based solution: factors influencing N>small<>sub<2>/small<>/sub<O emissions in tropical soils

“…The variability in the N2O-biochar interaction is due to the influence of several factors, some of them linked to soil management practices, N fertilizer rate and type, presence of organic residues, soil pH, and biochar application rate (Boateng et al, 2020;Feng et al, 2018;Wang et al, 2018;Wu et al, 2018). Moreover, the physicochemical properties of biochar (e.g., feedstock material, pyrolisis temperature, C: N ratio, N content, surface area, and pH) may also affect the response of N2O emissions (Kollah et al, 2022;Liao et al, 2021;. Because of the relationship among these variables, the sum between them will modulate the response of soil-plantatmosphere system to its use as a soil amendment.…”