Department of Earth, Ocean and Atmospheric Sciences, The University of British Columbia, Vancouver, British Columbia V6T 1Z4 Canada
Institute for Resources, Environment and Sustainability, The University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
Steve W. Lyon
Department of Physical Geography, Stockholm University, Stockholm, Sweden
Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
School 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.
This preprint has been withdrawn.
How to cite. Fischer, B. M. C., Morillas, L., Rojas Conejo, J., Sánchez-Murillo, R., Suárez Serrano, A., Frentress, J., Cheng, C.-H., Garcia, M., Manzoni, S., Johnson, M. S., and Lyon, S. W.: Investigating the impacts of biochar on water fluxes in tropical agriculture using stable isotopes, Hydrol. Earth Syst. Sci. Discuss. [preprint], https://doi.org/10.5194/hess-2020-404, 2020.
Received: 05 Aug 2020 – Discussion started: 20 Aug 2020
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.
We investigated in an upland rice experiment in Costa Rica whether mixing biochar (a charcoal)...