title: Impact of elevated CO2 and temperature on soil C and N dynamics in relation to CH4 and N2O emissions from tropical flooded rice (Oryza sativa L.).
abstract: A field experiment was carried out to investigate the impact of elevated carbon dioxide (CO2) (CEC, 550 μmol mol(-1)) and elevated CO2+elevated air temperature (CECT, 550 μmol mol(-1) and 2°C more than control chamber (CC)) on soil labile carbon (C) and nitrogen (N) pools, microbial populations and enzymatic activities in relation to emissions of methane (CH4) and nitrous oxide (N2O) in a flooded alluvial soil planted with rice cv. Naveen in open top chambers (OTCs). The labile soil C pools, namely microbial biomass C, readily mineralizable C, water soluble carbohydrate C and potassium permanganate oxidizable C were increased by 27, 23, 38 and 37% respectively under CEC than CC (ambient CO2, 394 μmol mol(-1)). The total organic carbon (TOC) in root exudates was 28.9% higher under CEC than CC. The labile N fractions were also increased significantly (29%) in CEC than CC. Methanogens and denitrifier populations in rhizosphere were higher under CEC and CECT. As a result, CH4 and N2O-N emissions were enhanced by 26 and 24.6% respectively, under CEC in comparison to open field (UC, ambient CO2, 394 μmol mol(-1)) on seasonal basis. The global warming potential (GWP) was increased by 25% under CEC than CC. However, emissions per unit of grain yield under elevated CO2 and temperature were similar to those observed at ambient CO2. The stimulatory effect on CH4 and N2O emissions under CEC was linked with the increased amount of soil labile C, C rich root exudates, lowered Eh, higher Fe(+2) concentration and increased activities of methanogens and extracellular enzymes.
authors.affiliation: Division of Crop Production, Central Rice Research Institute, Cuttack, 753006, Odisha, India. pratap162001@yahoo.co.in
authors.forename: P
authors.initials: P
authors.lastname: Bhattacharyya
authors.forename: K S
authors.initials: KS
authors.lastname: Roy
authors.forename: S
authors.initials: S
authors.lastname: Neogi
authors.forename: P K
authors.initials: PK
authors.lastname: Dash
authors.forename: A K
authors.initials: AK
authors.lastname: Nayak
authors.forename: S
authors.initials: S
authors.lastname: Mohanty
authors.forename: M J
authors.initials: MJ
authors.lastname: Baig
authors.forename: R K
authors.initials: RK
authors.lastname: Sarkar
authors.forename: K S
authors.initials: KS
authors.lastname: Rao
mesh_terms: D000383:Agriculture; D002244:Carbon / Q000378:metabolism; D002245:Carbon Dioxide / Q000032:analysis; D002849:Chromatography, Gas; D057232:Global Warming; D007194:India; D007501:Iron / Q000378:metabolism; D008697:Methane / Q000378:metabolism; D009584:Nitrogen / Q000378:metabolism; D009609:Nitrous Oxide / Q000378:metabolism; D012275:Oryza / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism; D012044:Regression Analysis; D058441:Rhizosphere; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013696:Temperature; D014329:Tropical Climate
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D007501:Iron; D009609:Nitrous Oxide; D009584:Nitrogen; D008697:Methane
keywords: CH(4) and N(2)O emissions; Elevated CO(2); Elevated temperature; Flooded rice; Soil labile C and N pools