Fulai Liu, Yanqi Sun
Department of Agriculture and Ecology,
Faculty of Life Sciences, University of Copenhagen

Biological water saving irrigation strategies such as regulated deficit irrigation (RDI) and alternate partial root-zone drying (PRD) irrigation have been intensively researched in the last two decades. Across several crop species including fruit trees, vegetables, and field crops, both RDI and PRD have shown great potential to save water and increase water use efficiency (WUE). In addition, accumulated evidence indicates that crops under PRD often over perform those under RDI suggesting that PRD had triggered different plant drought adaptation mechanisms in relation to the RDI treatment. The drying/wetting cycles of the soil profile under the PRD treatment could induce the ‘Birch effect’ stimulating mineralization of soil organic carbon (C) and nitrogen (N). On one hand, it may increase the mineral N availability for plant uptake thereby increasing N use efficiency; on the other hand it may increase the soil respiration rates hence enhancing C losses into the atmosphere. Therefore, it is questionable that if PRD is an environmentally friendly irrigation practice in terms of soil C sequestration. Further studies are necessary to explore the mechanisms by which the C and N dynamics in the soil-plant system are affected by different water-saving irrigation strategies.