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Title: Diel plant water use and competitive soil cation exchange interact to enhance NH 4 + and K + availability in the rhizosphere

Hydro-biogeochemical processes in the rhizosphere regulate nutrient and water availability, and thus ecosystem productivity. We hypothesized that two such processes often neglected in rhizosphere models — diel plant water use and competitive cation exchange — could interact to enhance availability of K + and NH 4 +, both high-demand nutrients. A rhizosphere model with competitive cation exchange was used to investigate how diel plant water use (i.e., daytime transpiration coupled with no nighttime water use, with nighttime root water release, and with nighttime transpiration) affects competitive ion interactions and availability of K + and NH 4 +. Competitive cation exchange enabled lowdemand cations that accumulate against roots (Ca 2+, Mg 2+, Na +) to desorb NH 4 + and K + from soil, generating non-monotonic dissolved concentration profiles (i.e. ‘hotspots’ 0.1–1 cm from the root). Cation accumulation and competitive desorption increased with net root water uptake. Daytime transpiration rate controlled diel variation in NH 4 + and K + aqueous mass, nighttime water use controlled spatial locations of ‘hotspots’, and day-to-night differences in water use controlled diel differences in ‘hotspot’ concentrations. Finally, diel plant water use and competitive cation exchange enhanced NH 4 + and K + availability and influencedmore » rhizosphere concentration dynamics. Demonstrated responses have implications for understanding rhizosphere nutrient cycling and plant nutrient uptake.« less
 [1] ;  [2] ;  [3] ;  [1]
  1. Univ. of Washington, Seattle, WA (United States). Dept. of Civil and Environmental Engineering
  2. Marine Biological Lab., Woods Hole, MA (United States). Ecosystems Center
  3. Univ. of British Columbia, Vancouver, BC (Canada). Dept. of Earth, Ocean and Atmospheric Sciences
Publication Date:
Grant/Contract Number:
Published Article
Journal Name:
Plant and Soil
Additional Journal Information:
Journal Volume: 414; Journal Issue: 1-2; Journal ID: ISSN 0032-079X
Research Org:
Marine Biological Lab., Woods Hole, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
54 ENVIRONMENTAL SCIENCES; Hydraulic redistribution; Nighttime transpiration; Plant nutrient uptake; Reactive-transport; Rhizosphere; Root water uptake
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1426163