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Quantification of plant water uptake by water stable isotopes in rice paddy systems

Authors
  • Mahindawansha, Amani1, 2
  • Orlowski, Natalie1, 3
  • Kraft, Philipp1
  • Rothfuss, Youri4
  • Racela, Heathcliff2
  • Breuer, Lutz1, 5
  • 1 Justus Liebig University Giessen, Institute for Landscape Ecology and Resources Management (ILR), Research Centre for BioSystems, Land Use and Nutrition (IFZ), Heinrich Buff ring 26-32, 35392 Giessen, Germany , 35392 Giessen (Germany)
  • 2 International Rice Research Institute (IRRI), Los Baños, Philippines , Los Baños (Philippines)
  • 3 Albert Ludwigs University of Freiburg, Chair of Hydrology, Faculty of Environment and Natural Resources, Freiburg im Breisgau, Germany , Freiburg im Breisgau (Germany)
  • 4 Institute of Bio- and Geosciences, IBG-3 Agrosphere, Forschungszentrum Jülich GmbH, Jülich, Germany , Jülich (Germany)
  • 5 Justus Liebig University Giessen, Centre for International Development and Environmental Research, Senckenbergstrasse 3, Giessen, D-35390, Germany , Giessen (Germany)
Type
Published Article
Journal
Plant and Soil
Publisher
Springer International Publishing
Publication Date
May 31, 2018
Volume
429
Issue
1-2
Pages
281–302
Identifiers
DOI: 10.1007/s11104-018-3693-7
Source
Springer Nature
Keywords
License
Yellow

Abstract

AimUnderstanding the source water utilization of rice-based cropping systems helps develop improving water management strategies for paddy management. We investigated the effects of altered flooding regimes and crop diversification on plant root water uptake on a fully-replicated field trial at the International Rice Research Institute in the Philippines.MethodsAll potential water pools, e.g., plant and soil extracted water, were analyzed for their water stable isotopic compositions (δ2H and δ18O). We determined the relative contributions from different water sources to root water uptake (RWU) of rice plants by applying a multi-source mixing model (Stable Isotopes Analysis in R, SIAR). The sensitivity of the model to the incorporation of prior information based on in-situ measurements of soil water content and root length density was investigated as well.ResultsThe modeling results showed that wet rice plants mainly extracted surface ponded water (~56–72%) during both wet and dry seasons followed by soil surface (0–0.02 m) water (~17–19%) during growth. Dry rice extracted ~40–50% of its water from shallow soil (0–0.5 m) and ~35% from 0.1 to 0.3 m depth when the plants were matured.ConclusionsThe mixing model results were better constrained with the additional information on soil water content and root length density. The relative contributions of the soil water sources to RWU decreased with depth and reflected the exponential shape of the root density profile. The main water source for wet rice was surface ponded water (independent of the season), whereas shallow soil water was the main source for dry rice.

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