Preprints
https://doi.org/10.5194/hess-2020-404
https://doi.org/10.5194/hess-2020-404

  20 Aug 2020

20 Aug 2020

Review status: this discussion paper is a preprint. It has been under review for the journal Hydrology and Earth System Sciences (HESS). The manuscript was not accepted for further review after discussion.

Investigating the impacts of biochar on water fluxes in tropical agriculture using stable isotopes

Benjamin M. C. Fischer1,2,3, Laura Morillas4, Johanna Rojas Conejo5, Ricardo Sánchez-Murillo6, Andrea Suárez Serrano5, Jay Frentress7,8, Chih-Hsin Cheng9, Monica Garcia10, Stefano Manzoni1,3, Mark S. Johnson11,12, and Steve W. Lyon1,3,13 Benjamin M. C. Fischer et al.
  • 1Department of Physical Geography, Stockholm University, Stockholm, Sweden
  • 2Department of Earth Sciences, Uppsala University, Uppsala, Sweden
  • 3Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 4Centre for Sustainable Food Systems, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
  • 5Water Resources Center for Central America and the Caribbean (HIDROCEC-UNA), Universidad Nacional de Costa Rica, Guanacaste
  • 6Stable Isotopes Research Group and Water Resources Management Laboratory, Universidad Nacional, Heredia, Costa Rica
  • 7Free University of Bolzano, Italy
  • 8Water Resources, Ramboll Sverige AB, Stockholm, Sweden
  • 9School of Forestry and Resource Conservation, National Taiwan University, Taipei, Taiwan
  • 10Department of Environmental Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
  • 11Department of Earth, Ocean and Atmospheric Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada
  • 12Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
  • 13School of Environment and Natural Resources, Ohio State University, Ohio, USA

Abstract. Amending soils with biochar, a pyrolyzed organic material, is an emerging practice to potentially increase plant available water. However, it is not clear (1) to what extent biochar amendments increase soil water storage relative to non-amended soils and (2) whether plants grown in biochar amended soils access different pools of water compared to those grown in non-amended soils. To investigate these questions, we set up an upland rice field experiment in a tropical seasonally dry region in Costa Rica, with plots treated with two different biochar amendments and control plots, from where we collected hydrometric and isotopic data (δ18O and δ2H from rain, soil, groundwater and rice plants). Our results show that the soil water retention curves for biochar treated soils shifted, indicating that rice plants had 2 % to 7 % more water available throughout the growing season relative to the control plots. In addition, we observed a within treatment variability in the soil water retention curves which was in the same order of magnitude as one would expect from responses due to differences in biochar application rates or due to differences in biochar typologies. The stable water isotope composition of plant water showed that the rice plants across all plots preferentially utilized the more variable soil water from the top 20 cm of the soil instead of using the deeper and less variable sources of water. Our results indicated that rice plants in biochar amended soils could access larger stores of water more consistently and thus could withstand dry spells of seven extra days relative to rice grown in non-treated soils. Though supplemental irrigation was required to facilitate plant growth during extended dry periods. Therefore, biochar amendments can complement, but not necessarily replace, other water management strategies.

Benjamin M. C. Fischer et al.

 
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Status: closed
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Benjamin M. C. Fischer et al.

Benjamin M. C. Fischer et al.

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Short summary
We investigated in an upland rice experiment in Costa Rica whether mixing biochar (a charcoal) in soils could increase the resilience of rainfed agriculture to climate variability. We found that rice plants with biochar had access to larger stores of water more consistently and thus could withstand seven extra dry days relative to rice grown in non-treated soils. However, biochar can complement, but not necessarily replace, other water management strategies.