Sustainable phosphorus management in soil using bone apatite.

Area of Science:

• Environmental Science
• Soil Science
• Biogeochemistry

Background:

• Bone apatite amendment is a promising strategy for soil fertility and phosphorus management.
• Understanding the long-term transformation of bone apatite in soil is crucial for optimizing its use.
• Integrating physicochemical and mineralogical changes with phosphorus dynamics requires further investigation.

Purpose of the Study:

• To investigate the 10-year transformation of bone apatite in field conditions.
• To elucidate the impact of bone apatite alteration on phosphorus supply and storage in soil.
• To correlate mineralogical and physicochemical changes with microbial decomposition and nutrient release.

Main Methods:

• Field study over 10 years utilizing synchrotron-based microscopic and spectroscopic techniques.
• Transmission X-ray microscopy (TXM) for in-situ observation of bone deterioration and microbial activity.
• X-ray Photoelectron Spectroscopy (XPS) to analyze mineral and organic component interactions.

Main Results:

• Early microbial tunneling and organic decomposition observed within the first year.
• Significant secondary mineral formation and apatite re-mineralization noted by the third year.
• Increased carbonate substitution and crystallographic rearrangement of hydroxyapatite over 10 years.
• Evidence of organo-mineral decoupling and demineralization leading to phosphorus release into the soil.
• Formation of amorphous, carbonate-substituted secondary minerals in lab incubations, prone to dissolution in acidic conditions.

Conclusions:

• Bone apatite undergoes significant microbial and mineralogical transformations over a decade in soil.
• These transformations facilitate a sustainable release and storage of phosphorus, enhancing soil fertility.
• Stage-dependent microbial decomposition and secondary mineral formation play key roles in phosphorus cycling.