Inorganic phosphorus fractionation and its translocation dynamics in a low-P soil

Area of Science:

• Soil Science
• Plant Nutrition
• Biogeochemistry

Background:

• Low-phosphorus (P) soil conditions limit crop productivity globally.
• Understanding inorganic phosphorus (Pi) dynamics is crucial for improving P availability and crop P-use efficiency.
• Plant-unavailable P fractions often dominate in deficient soils, exacerbating P scarcity.

Purpose of the Study:

• To investigate the transformation and availability of different inorganic phosphorus (Pi) forms in a low-P soil.
• To assess the soil P availability and maize genotype-specific P-use efficiency.
• To elucidate the impact of P fertilization on Pi transformation pathways.

Main Methods:

• Phosphorus fractionation extraction was employed to determine soil Pi composition.
• A (32)P tracer technique tracked the transformation of inorganic phosphorus (Pi) over time.
• Maize L-value determination assessed P availability and genotype-specific P-use efficiency.

Main Results:

• Plant-unavailable P fractions (Ca(10)-P and O-P) constituted a high proportion (79.1%) of total Pi in the low-P soil.
• In unfertilized soil, added (32)P-Pi rapidly transformed into Ca(2)-P (29.0%) and slowly available forms (Al-P, Fe-P, Ca(8)-P; 66.1%).
• P fertilization increased the transformation of (32)P-Pi into rapidly available Ca(2)-P and decreased its conversion to slowly available and unavailable forms, indicating faster P fixation in fertilized low-P soil.

Conclusions:

• High levels of plant-unavailable P contribute significantly to P deficiency in the studied soil.
• Water-soluble P transforms more readily into slowly available and unavailable forms in P-deficient soils compared to P-sufficient soils.
• Different maize genotypes display distinct P-use efficiencies and low-P tolerance mechanisms, highlighting the potential for breeding improved cultivars.