Copper phytoavailability in vineyard topsoils as affected by pyoverdine supply.

Area of Science:

• Environmental Science
• Soil Science
• Biogeochemistry

Background:

• Pyoverdine (Pvd) is a siderophore produced by Pseudomonads, capable of binding copper (Cu) and iron (Fe) in soils.
• Pvd's influence on Cu dynamics and ecotoxicity in vineyard soils is largely unknown.
• Understanding Cu mobility and phytoavailability in vineyard soils is crucial for managing soil health and plant uptake.

Purpose of the Study:

• To investigate how soil pH affects Cu mobility and phytoavailability in vineyard soils.
• To determine the impact of Pvd supply on Cu mobility and phytoavailability across a range of soil pH.
• To assess the potential of Pvd-producing bacteria for enhancing Cu phytoextraction.

Main Methods:

• Ten vineyard topsoils with varying pH (5.9–8.6) were treated with and without Pvd.
• Copper (Cu) mobility was assessed via total Cu concentration in CaCl2 extracts.
• Cu phytoavailability was measured as the free ionic concentration (Cu2+) in CaCl2 extracts.

Main Results:

• Cu mobility varied by a factor of six, while phytoavailability varied by 5000-fold among soils.
• Cu2+ concentration correlated with soil pH, not total Cu, indicating pH-dependent complexation.
• Pvd addition enhanced Cu mobility (1.4–8 fold) but reduced Cu2+ concentrations in extracts.

Conclusions:

• Cu phytoavailability in vineyard soils is primarily governed by pH-dependent complexation in soil pore water.
• Pvd enhances Cu mobility by increasing its solubility in soil.
• The addition of Pvd reduces Cu2+ availability, contradicting its proposed use for promoting Cu phytoextraction.