Greenhouse Gas Emission of Different Crop Rotations of Rice (flooded and non-flooded) and Maize
Final Report Abstract
For a comprehensive assessment of greenhouse gas (GHG) balances, we measured methane (CH4) nitrous oxide (N2O) emissions and agronomic parameters over 6 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 N2O emissions increased two- to threefold in diversified rice systems, the strong reduction in CH4 emission led to a significantly lower (P < 0.05) annual Global Warming Potential (GWP) as compared to the traditional double-rice cropping system. Adequate irrigation schemes have a high potential to reduce N2O emissions during upland cropping. We investigated if straw residue incorporation and/or catch crop cultivation impairs the greenhouse gas footprint of diversifying rice cropping systems and thus offers an alternative to open-field straw burning: Due to strong reduction in CH4 emissions lowest GWP for rice-maize (R-M) cropping systems, followed by R-A and R-R systems persists also with the incorporation of crop residues (straw and straw + mung bean), a requirement for farmers as the ban of open-field burning is increasingly enforced. Application of organic amendments increased substrate availability for methanogens and associated CH4 emissions during the following wet rice season. Thus, GWP was 9-39% higher in treatments including straw incorporation as compared to control treatments without organic substrate amendments. Surface application rather than incorporation and straw application during DS in diversified paddy rice upland crop rotations (R-M, R-A) lead to lowest increases in soil CH4 emissions. Additional incorporation of mung beans (straw + mung beans) further increased GWP, with highest increment in R-R (88%) and lowest in R-M rotation (55%). Compared to the traditional R-R system the R-M system with moderate organic residue applications allows for reducing irrigation water and GWP, which is important considering the expansion of diversified rice cropping systems in SE Asia. Our study shows that land-preparation and fallow periods substantially contribute to seasonal CH4 and N2O emissions and need to be considered when assessing / comparing GWPs of rice systems. Our work calls for a refinement of IPCC emission factors for lowland-upland rice rotations, application of organic amendments and the inclusion of the land-preparation periods within the GHG balance of rice cropping systems. Overall, methane (CH4) emissions from rice paddies often show significant diurnal variations, most likely driven by diurnal changes of radiation and temperature in air, floodwater, and soil: Disregarding the diurnal variability of fluxes results in an average overestimation of seasonal CH4 emissions of 22% (16–31%) if measurements were conducted only around noon, likely to happen with manual chamber sampling schemes. Scheduling manual sampling either at early morning (7:00–9:00) or evening (17:00–19:00) results in estimations of seasonal emissions within 94–101% of the ‘‘true’’ value as calculated from multiple daily flux measurements, an important information currently integrated into CH4 emission measurement protocols. In this context, we also provide correction factors, to convert flux rates to daily representative values at any sampling time of the day.
Publications
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(2014). Methane and nitrous oxide emissions from rice and maize production in diversified rice cropping systems. Nutrient Cycling in Agroecosystems 101, 37-53
Weller S., Kraus D., Ayag K., Wassmann R., Alberto M., Butterbach-Bahl K., Kiese R.
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(2015). A new LandscapeDNDC biogeochemical module to predict CH4 and N2O emissions from lowland rice and upland cropping systems. Plant and Soil 386, 125-149
Kraus D., Weller S., Klatt S., Haas E., Wassmann R., Kiese R., Butterbach-Bahl K.
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(2015). Diurnal patterns of methane emissions from paddy rice fields at the Philippines. Journal of Plant Nutrition and Soil Science
Weller, S., Kraus, D., Butterbach-Bahl, K., Wassmann, R., Tirol-Padre, A., Kiese, R.
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(2015). Greenhouse gas emissions of different crop rotations of rice (flooded and nonflooded) and maize. Albert-Ludwigs-Universität Freiburg, Fakultät für Umwelt und natürliche Ressourcen, Dissertation, 47 p.
Weller S.
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(2016). Greenhouse gas emissions and global warming potential of traditional and diversified tropical rice rotation systems. Global Change Biology 22
Weller, S., Janz, B., Jörg, L., Kraus, D., Racela, H.S.U., Wassmann, R., Butterbach-Bahl, K., Kiese, R.
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(2016). How well can we assess impacts of agricultural land management changes on the total greenhouse gas balance (CO2, CH4 and N2O) of tropical rice-cropping systems with a biogeochemical model? Agriculture Ecosystem and Environment 224, 104-115
Kraus D., Weller S., Klatt S., Santabárbara I., Haas E., Wassmann R., Werner C., Kiese R., Butterbach- Bahl K.
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(2019). Greenhouse gas footprint of diversifying rice cropping systems: Impacts of water regime and organic amendments. Agriculture Ecosystem and Environment 270-271, 41-54
Janz B., Weller S., Kraus D., Racela H.S., Wassmann R., Butterbach-Bahl K., Kiese R.
