EGU General Assembly 2022
© Author(s) 2022. This work is distributed under
the Creative Commons Attribution 4.0 License.

Effect of N fertilizer amount and water management on CO2 exchange and net ecosystem C balance of rice cultivation in Southern Benin

Leonce Geoffroy Sossa1,3,4, Jesse Naab1, Jürgen Augustin2, Luc Sintondji3, Souleymane Sanogo4, and Mathias Hoffmann2
Leonce Geoffroy Sossa et al.
  • 1West African Science Service Center on Climate Change and Adapted Land Use (WASCAL), 06 BP 9507 Ouaga 06, Ouagadougou, Burkina Faso
  • 2Leibniz Centre for Agricultural Landscape Research (ZALF), Isotope Biogeochemistry and Gas Fluxes, Eberswalder Straße 84, 15734 Müncheberg, Germany
  • 3Laboratoire d'Hydraulique et de Maitrise de l'Eau (LHME), Université d’Abomey-Calavi, 01 BP 526,Abomey-Calavi , Benin
  • 4Université des Sciences, des Techniques et des Technologies de Bamako ( USTTB), BP E 423, Bamako, Mali

Application of mineral nitrogen (N) fertilizer and water management are two very essential farming practices, used to optimize potential yields in sub-Sahara African rice cultivation. Differences in both practices, however, might affect the patterns of climate relevant gaseous carbon (C) emissions (CO2 and CH4) and soil C losses, thus contributing to global climate change. To date, knowledge about the combined effects of different N fertilizer rates together with different water management practices on the gaseous C emissions and soil C losses are very limited. This is even more the case for arable lands in sub-Sahara Africa. Our study aims to identify the best combination of water management and N fertilizer amount to reduce gaseous C emissions and limit soil C losses for an irrigated rice production in Benin. We hypothesize that especially a combination of alternate wetting and drying (AWD) as water management and an optimum amount of N fertilizer reduce gaseous C emissions and might help to enhance C sequestration by reducing soil C losses from irrigated rice production in Benin. To test this hypothesis, a field experiment was established at Koussin lélé, Cove district, southern Benin using a full factorial, split-plot experimental design. Within the experiment the combination of three levels of water management and two levels of N fertilizer amount are tested. The water management technologies include continuous flooding (CF) and two alternate wetting and drying (AWD) methods (AWD15 and AWD25) of irrigation. Nitrogen fertilizer levels is 90 kg/ha (farmer’s practice) and 120 kg/ha (high amount of fertilizer). To measure gaseous C emissions (CO2 and CH4) and estimate dynamics in soil C losses, an innovative, customized low cost dynamic NFT-NSS closed chamber system is used. The system consists of CO2/CH4 NDIR sensors connected to a microcontroller for data storage and transparent (NEE measurements) polycarbonate chambers (40 cm x 40 cm x 100 cm). To measure Reco, transparent chambers where covered with an opaque hood. Chamber measurements for diurnal variability in CH4 and CO2 fluxes are performed biweekly at all plots. In addition, agronomy and crop growth indices such as the Normalized difference vegetation index (NDVI) are measured weekly. Here we present CO2 and NECB balances for the first crop growth period.

Key words: Water management, N fertilizer, CO2 emission, net ecosystem carbon balance (NECB), rice

How to cite: Sossa, L. G., Naab, J., Augustin, J., Sintondji, L., Sanogo, S., and Hoffmann, M.: Effect of N fertilizer amount and water management on CO2 exchange and net ecosystem C balance of rice cultivation in Southern Benin, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-232,, 2022.