Inoculation of plant growth promoting-methane utilizing bacteria in different N-fertilizer regime influences methane emission and crop growth of flooded paddy

Abstract

Methane (CH₄) emission in rice fields is greatly influenced by the type and quantity of nitrogenous fertilizer used. The net methane emission from paddy fields is also influenced by the activity of methane utilizing bacteria, which inhabit the flooded paddy ecosystem. Efficient methane utilizing and plant growth promoting bacteria Methylobacterium oryzae MNL7 and Paenibacillus polymyxa MaAL70, respectively were co-inoculated along with different nitrogenous fertilizer combinations in flooded paddy to assess their impact on cumulative methane emission and crop growth promotion. Co-inoculation significantly influenced the plant growth parameters of paddy, resulting in an increase in grain yield by 14.04, 11.08, and 12.38% in treatments receiving Urea, Di-ammonium Phosphate (DAP) + Urea, or farm yard manure (FYM), over their respective un-inoculated plots. Significant improvement in the rice grain nutrient quality in term of crude protein, Fe and Zn content was observed as a result of bacterial co-inoculation in FYM fertilized plots as compared to Urea and DAP+ Urea fertilized plots. Significantly higher cumulative methane emission of 63.39 kg ha^-1 was observed in uninoculated plots fertilized with FYM treatment as compared to Urea (33.83 kg ha^-1) and DAP+Urea (31.66 kg ha^-1) treatments. Bacterial co-inoculation significantly reduced the cumulative methane emission by 12.03, 11.47 and 6.92% in Urea, DAP+Urea, and FYM fertilized plots over their respective uninoculated treatments. Among the different fertilizer treatments, bacterial co-inoculation with urea application performed significantly better in reducing cumulative methane emission. These findings suggest that methane utilizing bacteria which also possess plant growth promoting trait can be explored for developing a novel biofertilizer for flooded paddies, as they can aid in managing both the overall methane emission and enhancing crop yield.

Keywords: Methane; Methane utilizing bacteria; Methylobacterium; Nitrogenous fertilizer; Paenibacillus; Rice.