Mitigation of yield-scaled greenhouse gas emissions from irrigated rice through Azolla, Blue-green algae, and plant growth-promoting bacteria

Environ Sci Pollut Res Int. 2021 Oct;28(37):51425-51439. doi: 10.1007/s11356-021-14210-z. Epub 2021 May 13.

Abstract

Irrigated transplanted flooded rice is a major source of methane (CH4) emission. We carried out experiments for 2 years in irrigated flooded rice to study if interventions like methane-utilizing bacteria, Blue-green algae (BGA), and Azolla could mitigate the emission of CH4 and nitrous oxide (N2O) and lower the yield-scaled global warming potential (GWP). The experiment included nine treatments: T1 (120 kg N ha-1 urea), T2 (90 kg N ha-1 urea + 30 kg N ha-1 fresh Azolla), T3 (90 kg N ha-1 urea + 30 kg N ha-1 Blue-green algae (BGA), T4 (60 kg N ha-1 urea + 30 kg N ha-1 BGA + 30 kg N ha-1 Azolla, T5 (120 kg N ha-1 urea + Hyphomicrobium facile MaAL69), T6 (120 kg N ha-1 by urea + Burkholderia vietnamiensis AAAr40), T7 (120 kg N ha-1 by urea + Methylobacteruim oryzae MNL7), T8 (120 kg N ha-1 urea + combination of Burkholderia AAAr40, Hyphomicrobium facile MaAL69, Methylobacteruim oryzae MNL7), and T9 (no N fertilizer). Maximum decrease in cumulative CH4 emission was observed with the application of Methylobacteruim oryzae MNL7 in T7 (19.9%), followed by Azolla + BGA in T4 (13.2%) as compared to T1 control. N2O emissions were not significantly affected by the application of CH4-oxidizing bacteria. However, significantly lower (P<0.01) cumulative N2O emissions was observed in T4 (40.7%) among the fertilized treatments. Highest yields were observed in Azolla treatment T2 with 25% less urea N application. The reduction in yield-scaled GWP was at par in T4 (Azolla and BGA) and T7 (Methylobacteruim oryzae MNL7) treatments and reduced by 27.4% and 15.2% in T4 and T7, respectively, as compared to the T1 (control). K-means clustering analysis showed that the application of Methylobacteruim oryzae MNL7, Azolla, and Azolla + BGA can be an effective mitigation option to reduce the global warming potential while increasing the yield.

Keywords: Methane; Mitigation; Nitrous oxide; Plant growth–promoting bacteria; Rice; Yield-scaled GWP emission.

MeSH terms

  • Agriculture
  • Burkholderia
  • Cyanobacteria*
  • Fertilizers / analysis
  • Global Warming
  • Greenhouse Gases* / analysis
  • Hyphomicrobium*
  • Methane / analysis
  • Nitrous Oxide / analysis
  • Oryza*
  • Soil

Substances

  • Fertilizers
  • Greenhouse Gases
  • Soil
  • Nitrous Oxide
  • Methane

Supplementary concepts

  • Burkholderia vietnamiensis
  • Hyphomicrobium facile