Water quality changes seasonal variations in root respiration, xylem CO2, and sap pH in citrus orchards

Indira Paudel, Asher Bar-Tal, Nativ Rotbart, Jhonathan Ephrath, Shabtai Cohen

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


Effects of treated wastewater (TWW) and fresh water (FW) on autotrophic belowground respiration and respiratory coefficients (Q10) in summer and winter were determined in a commercial citrus orchard. Efflux of CO2 from soil and the often-ignored CO2 transported in xylem sap were quantified; the latter derived from sap flux, CO2 concentration ([CO2]), pH, and temperature. Xylem [CO2] scaled with xylem sap flux, pH and temperature. TWW and summer increased xylem sap pH (by 12% and 19%), soil CO2 efflux (32% and 65%), and root respired CO2 (10–15% and 55%) in comparison to FW and winter, respectively. About twice as much CO2 from the below ground autotrophic portion of respiration moved in xylem sap as compared to that diffused from the roots into the soil, with seasonal variations of about ±10%. Maximum temperature-dependent respiratory coefficients (Q10) were 4.7 for autotrophic root respiration and 3.8 for bulk soil CO2 efflux, and values varied with water quality and season. Total below ground respiration exceeds that previously reported and is a large part of the tree's carbon balance. Increased respiratory losses caused by poor quality water may explain reduced orchard root growth and overall productivity.

Original languageEnglish
Pages (from-to)147-157
Number of pages11
JournalAgricultural Water Management
StatePublished - 15 Jan 2018


  • Autotrophic
  • Effluent
  • Greenhouse gas emission
  • Heterotrophic
  • Waste water

ASJC Scopus subject areas

  • Agronomy and Crop Science
  • Water Science and Technology
  • Soil Science
  • Earth-Surface Processes


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