Phosphorus availability for plant uptake in a phosphorus-enriched noncalcareous sandy soil

Area of Science:

• Soil Science
• Environmental Chemistry
• Agronomy

Background:

• Phosphorus (P)-enriched soils pose a risk of P leaching.
• Mining soil phosphorus, through crop uptake without external P addition, is a proposed management strategy.
• Understanding long-term soil P availability is crucial for effective management.

Purpose of the Study:

• To evaluate the effectiveness of mining soil phosphorus in reducing P in different soil pools.
• To determine the long-term availability of soil phosphorus in P-enriched sandy soil.
• To assess the impact of soil layer thickness on P mining efficiency.

Main Methods:

• A 978-day greenhouse pot experiment with grass grown on P-enriched soil at zero P application.
• Analysis of soil phosphorus in solution (0.01 M CaCl2 extracts) and sorbed P (P(ox)).
• Construction of desorption isotherms using the Langmuir equation to model P availability.

Main Results:

• Plant uptake can remove up to 65% of the total acid ammonium oxalate-extractable phosphorus (P(ox)) over the long term.
• The Langmuir equation accurately described the P desorption isotherm, indicating P(ox) is largely plant-available.
• Mining soil phosphorus significantly decreased P concentration in soil solution, reducing leaching risk.

Conclusions:

• Mining soil phosphorus is an effective strategy for reducing P concentration in soil solution in P-enriched soils.
• Long-term plant uptake can deplete a substantial portion of soil P, mitigating leaching risks.
• The strong nonlinearity of the desorption isotherm explains the greater relative decrease in soil solution P compared to P(ox).