title: Greenhouse gas emissions and global warming potential of traditional and diversified tropical rice rotation systems.
abstract: Global rice agriculture will be increasingly challenged by water scarcity, while at the same time changes in demand (e.g. changes in diets or increasing demand for biofuels) will feed back on agricultural practices. These factors are changing traditional cropping patterns from double-rice cropping to the introduction of upland crops in the dry season. For a comprehensive assessment of greenhouse gas (GHG) balances, we measured methane (CH4 )/nitrous oxide (N2 O) emissions and agronomic parameters over 2.5 years in double-rice cropping (R-R) and paddy rice rotations diversified with either maize (R-M) or aerobic rice (R-A) in upland cultivation. Introduction of upland crops in the dry season reduced irrigation water use and CH4 emissions by 66-81% and 95-99%, respectively. Moreover, for practices including upland crops, CH4 emissions in the subsequent wet season with paddy rice were reduced by 54-60%. Although annual N2 O emissions increased two- to threefold in the diversified systems, the strong reduction in CH4 led to a significantly lower (P < 0.05) annual GWP (CH4  + N2 O) as compared to the traditional double-rice cropping system. Measurements of soil organic carbon (SOC) contents before and 3 years after the introduction of upland crop rotations indicated a SOC loss for the R-M system, while for the other systems SOC stocks were unaffected. This trend for R-M systems needs to be followed as it has significant consequences not only for the GWP balance but also with regard to soil fertility. Economic assessment showed a similar gross profit span for R-M and R-R, while gross profits for R-A were reduced as a consequence of lower productivity. Nevertheless, regarding a future increase in water scarcity, it can be expected that mixed lowland-upland systems will expand in SE Asia as water requirements were cut by more than half in both rotation systems with upland crops.
authors.affiliation: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467, Garmisch-Partenkirchen, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Weller
authors.affiliation: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467, Garmisch-Partenkirchen, Germany.
authors.forename: Baldur
authors.initials: B
authors.lastname: Janz
authors.affiliation: Technical University Munich (TUM), Arcisstraße 21, 80333, Munich, Germany.
authors.forename: Lena
authors.initials: L
authors.lastname: Jörg
authors.affiliation: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467, Garmisch-Partenkirchen, Germany.
authors.forename: David
authors.initials: D
authors.lastname: Kraus
authors.affiliation: International Rice Research Institute (IRRI), Los Baños, Philippines.
authors.forename: Heathcliff S U
authors.initials: HS
authors.lastname: Racela
authors.affiliation: International Rice Research Institute (IRRI), Los Baños, Philippines.
authors.forename: Reiner
authors.initials: R
authors.lastname: Wassmann
authors.affiliation: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467, Garmisch-Partenkirchen, Germany.|International Livestock Research Institute (ILRI), 30709 Naivasha Road, Nairobi, Kenya.
authors.forename: Klaus
authors.initials: K
authors.lastname: Butterbach-Bahl
authors.affiliation: Karlsruhe Institute of Technology, Institute of Meteorology and Climate Research (IMK-IFU), Kreuzeckbahnstr. 19, 82467, Garmisch-Partenkirchen, Germany.
authors.forename: Ralf
authors.initials: R
authors.lastname: Kiese
mesh_terms: D057914:Agricultural Irrigation; D000383:Agriculture / Q000379:methods*; D000393:Air Pollutants / Q000032:analysis; D057232:Global Warming; D017752:Greenhouse Effect; D008697:Methane / Q000032:analysis; D009609:Nitrous Oxide / Q000032:analysis; D012275:Oryza / Q000254:growth & development / Q000378:metabolism*; D012621:Seasons; D012987:Soil / Q000737:chemistry; D003313:Zea mays / Q000254:growth & development / Q000378:metabolism
chemical_list: D000393:Air Pollutants; D012987:Soil; D009609:Nitrous Oxide; D008697:Methane
keywords: aerobic rice; maize; methane; nitrous oxide; paddy rice; rice rotation systems, economy; yield-scaled GWP