Tropentag, October 11 - 13, 2006 in Bonn "Prosperity and Poverty in a Globalized World – Challenges for Agricultural Research"

Greenhouse Gas Emissions from Irrigated Agriculture in Khorezm Region (Uzbekistan)

¹Center for Development Research, Bonn, Department of Ecology and Natural Resource Management, Germany
²Karlsruhe Research Center, Institute for Meteorology and Climate Research, Germany
³Center for Development Research (ZEF), University of Bonn, Germany

Abstract

Agricultural systems in the Khorezm region (Uzbekistan, Central Asia) are characterised by monocultures under irrigation in combination with intensive fertilisation. Irrigation and fertilisation of arid systems not only stimulates plant growth, but also a variety of microbial processes enhancing the turn-over of soil carbon and nitrogen (N) leading to elevated emissions of greenhouse gases (GHG) such as N₂O and CH₄.
In 2005, GHG emissions were measured from experimental fields at 6 research sites, encompassing 5 different land use types. Emission rates from irrigated agricultural fields were high and represent a significant source of GHG due to N₂O emissions from cotton and winter wheat as well as CH₄ emissions from flooded rice fields. Even an unfertilised plantation of poplar trees showed surprisingly high N₂O fluxes. In contrast, N₂O emissions were very low in spots with native vegetation, i.e. the ‘Baday Tugai' riparian forest along the Amu Darya River.
The observed temporal patterns of N₂O emissions were similar for cotton and winter wheat fields. Periods of very high N₂O emissions were triggered by fertiliser application in combination with irrigation. These “emission peaks” accounted for 80% of the total N₂O emissions over one cotton season. Cumulative N₂O emissions during the cropping season varied between 2.5kg N₂O-Nha^-1 - 5.6kg N₂O-Nha^-1, which corresponds to 3.8% of the total fertiliser applied.
The common management practice of concomitant fertilisation/irrigation in combination with the high soil temperatures during the season leads to an elevated soil microbial activity. Subsequently, the farming systems in Khorezm experience high losses of N via denitrification. This implies low N use efficiency of the fertiliser applied and large emissions of N₂O-gas. Modifications in the amount and timing and modalities of the fertiliser application in combination with improved irrigation techniques may improve the agronomic performance and reduce the environmental impacts.

Keywords: Emission, fertilisation, greenhouse gas, irrigation, N₂O

Contact Address: Clemens Scheer, Center for Development Research, Bonn, Department of Ecology and Natural Resource Management, Kreuzeckbahnstr. 19, D-82467 Garmisch-partenkirchen, Germany, e-mail: clemensscheerhotmail.com