Root Exudates Alters Nutrient Transport in Soil

Amit Paporisch*, Harel Bavli, Rachel J. Strickman, Rebecca B. Neumann, Nimrod Schwartz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

Abstract

Root exudates alter the rhizosphere's physical properties, but the impact that these changes have on solute transport is unknown. In this study, we tested the effects of chia mucilage and wheat root exudates (WREs) on the transport of iodide and potassium in saturated or unsaturated soil. Saturated solute breakthrough experiments, conducted in loamy sand soil or coarser textured quartz sand, revealed that increasing the exudate concentration in soil resulted in non-equilibrium solute transport. This behavior was demonstrated by an initial solute breakthrough after fewer pore volumes (PVs) and the arrival of the peak solute concentration after greater PVs in soil mixed with exudates compared to soil without exudates. These patterns were more pronounced for the coarser textured quartz sand than for the loamy sand soil, and in soil mixed with mucilage than in soil mixed WREs. Parameter fits to these breakthrough curves with a mobile-immobile transport model indicated the fraction of immobile water increased as the concentration of exudates increased. For example, in quartz sand the estimated immobile fraction increased from 0 without exudates to 0.75 at a mucilage concentration of 0.2%. The solutes' breakthrough under unsaturated conditions was also altered by the exudates, demonstrated by a smaller volume of water extracted from soil mixed with exudates, compared to soil without exudates, before the arrival of the peak solute concentration. The results indicate that exudates alter the rhizosphere's transport properties; we hypothesize that this is due to exudates creating low-conducting flow paths that result in a physical non-equilibrium solute transport.

Original languageAmerican English
Article numbere2021WR029976
JournalWater Resources Research
Volume57
Issue number10
DOIs
StatePublished - Oct 2021

Bibliographical note

Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.

Keywords

  • mucilage
  • nutrient transport
  • rhizosphere
  • root exudates
  • transport models

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