Relation between various soil phosphorus extraction methods and sorption parameters in calcareous soils with...

Area of Science:

• Soil Science
• Environmental Chemistry
• Agronomy

Background:

• Phosphorus (P) is a vital nutrient for plant growth, but its availability in soil is influenced by various factors.
• Calcareous soils, common in arid and semi-arid regions, often exhibit complex P dynamics due to high calcium carbonate content.
• Understanding P extractability and sorption is crucial for efficient fertilizer management and preventing environmental pollution.

Purpose of the Study:

• To investigate the influence of soil texture on phosphorus extractability and sorption in calcareous soils.
• To compare the effectiveness of different P extraction methods in assessing P availability.
• To identify key soil properties controlling P dynamics and provide recommendations for soil management.

Main Methods:

• Selected 57 soil samples from Hamedan, Iran, categorized into five textural classes.
• Extracted phosphorus using five methods: calcium chloride (PCaCl2), citrate (Pcitrate), HCl (PHCl), Olsen (POls), and Mehlich-3 (PM3).
• Analyzed soil phosphorus buffer capacity (PBC), sorption coefficients (KF, Qmax, Kd), and employed principal component analysis (PCA).

Main Results:

• Phosphorus extractability varied among methods, with the order PHCl > PM3 > Pcitrate > POls > PCaCl2 on average.
• Sandy, sandy clay loam, and sandy loam soils showed higher P extraction than clay and mixed loam soils.
• Silt content positively correlated with P sorption (KF, Qmax, Kd) and PBC, indicating its critical role.
• Indices like DPSM3-2 and DPScitrate indicated potential P release, with 21% of soils exceeding environmental thresholds.

Conclusions:

• Soil texture, particularly silt content, is a key determinant of phosphorus sorption and extractability in calcareous soils.
• Different P extraction methods provide varying insights into P availability, with DPS indices showing potential for assessing P release.
• Management practices are needed to mitigate P losses, especially in sandy clay loam soils with high P concentrations, and reduce fertilizer inputs where P has accumulated.