Organic matter and salinity modify cadmium soil (phyto)availability.

Area of Science:

• Environmental Science
• Soil Science
• Plant Nutrition

Background:

• Cadmium (Cd) availability in soil is complex, influenced by total concentration, mobility, transformations, and speciation.
• Pedovariables like soil organic matter (SOM) and salinity significantly affect Cd mobility through complex formation.
• Phytoavailable Cd is the fraction accessible and available for plant uptake, crucial for understanding metal bioavailability.

Purpose of the Study:

• To investigate the impact of varying soil organic matter (SOM) and NaCl salinity levels on cadmium (Cd) availability and phytoavailability in faba bean.
• To determine how SOM and salinity affect Cd speciation and mobility in the soil rhizosphere.
• To understand the relationship between total Cd concentration and its plant-available fraction under different soil conditions.

Main Methods:

• Greenhouse pot experiment using faba bean.
• Application of different levels of SOM, NaCl salinity (50 and 100mM), and Cd contamination (5 and 10mgkg⁻¹).
• Analysis of Cd availability, speciation, and phytoavailability in the soil rhizosphere.

Main Results:

• Cd availability in soil did not linearly correlate with its total concentration.
• Increased SOM reduced Cd phytoavailability, promoting Cd-organic matter complex formation.
• NaCl salinity decreased Cd soil and phytoavailability by promoting Cd-chloride complex formation, acting as a carrier rather than increasing availability.

Conclusions:

• Soil organic matter and salinity are critical factors controlling Cd phytoavailability, independent of total Cd concentration.
• Salinity-induced Cd chloro-complexes facilitate transfer between soil fractions but do not necessarily increase plant uptake.
• Understanding Cd speciation is key to predicting its bioavailability and managing potential risks in contaminated soils.