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Tropentag, September 14 - 16, 2022, Prague

"Can agroecological farming feed the world? Farmers' and academia's views."

Soil respiration under different N fertilisation and irrigation regimes in Bengaluru, India

Suman Kumar Sourav1, Chickadibburahalli T. Subbarayappa2, Prem Jose Vazhacharickal1, Andrea Mock1, Andreas Buerkert1

1University of Kassel, Organic Plant Production and Agroecosyst. Res. in the Tropics and Subtropics, Germany
2University of Agricultural Sciences, Dept. of Soil Sci. and Agricultural Chemistry, India


Rampant urbanisation has led to different levels of agricultural management intensities/practices in Urban and Peri-Urban Agriculture (UPA) which affects the soils’ physical, chemical, and microbial properties. This study was conducted to investigate the effects of different mineral nitrogen (N) fertiliser levels and irrigation on CO2 fluxes in typical crops during the Kharif (wet) and Rabi (dry) season under the typical monsoonal climate of Bengaluru, South India.
Data were collected in a two-factorial split-plot experiment conducted under rainfed and irrigated conditions in on-station experimental plots in University of Agricultural Sciences Bangalore (UASB). Investigated where the three rainfed crops maize (Zea mays L.), finger millet (Eleusine coracana Gaertn.), and lablab (Lablab purpureus L. Sweet) as well as irrigated cabbage (Brassica oleracea var. capitata), eggplant (Solanum melongena L.), and chili (Capsicum annuum L.). CO2 emissions were determined using a ventilated closed-chamber system connected to a Los Gatos Research (LGR) multi-gas analyzer (CO2, CH4, NH3 and H2O). Measurements were conducted in the morning hours from 7:00 am to 11:30 am and repeated from 1:00 pm to 6:00 pm.
Under irrigated conditions maize had 78 % lower CO2 soil emissions than lablab and 79 % lower in comparison with finger millet. Soil respiration in rainfed maize was 51 % higher than in irrigated maize and rainfed finger millet had 18 % higher values than irrigated finger millet. Under rainfed conditions high N maize plots had 104 % higher CO2 fluxes than maize without N. Similarly, in rainfed finger millet, CO2 emissions on high N plots were 31 % higher than on controls. In the Rabi season flux rates did not significantly differ between chili, cabbage and eggplant across fertiliser rates.
The results indicate that crop-specific CO2 fluxes were independent of N fertilisation under irrigation but were remarkably consistent across years. Under rainfed conditions CO2 emissions on high N plots were significantly higher than on plots without N.

Keywords: CO2 flux, fertiliser treatment, multi-gas analyzer, seasonal CO2 emissions

Contact Address: Suman Kumar Sourav, University of Kassel, Organic Plant Production and Agroecosyst. Res. in the Tropics and Subtropics, Steinstraße 19, 37213 Witzenhausen, Germany, e-mail: sourav.suman@gmail.com

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