Dynamic Changes in Soil Phosphorus Accumulation and Bioavailability in Phosphorus-Contaminated Protected Fields.

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Science

Background:

• Protected field agriculture often involves high cropping intensity and excessive phosphorus (P) fertilizer application, leading to soil P accumulation and environmental risks.
• Understanding the bioavailability of accumulated soil P is crucial for optimizing fertilization strategies and mitigating P pollution in these systems.

Purpose of the Study:

• To investigate the changes in soil phosphorus fractions and bioavailability under continuous spinach cultivation without P fertilizer application.
• To establish a model for predicting soil available phosphorus dynamics and guiding rational P fertilization in protected fields.

Main Methods:

• A field trial was conducted in Yanbian Prefecture, China, involving continuous spinach planting.
• Soil samples were analyzed for various phosphorus fractions (inorganic P, occluded P, water-soluble and loose P, Al-P, Fe-P, Ca-P) and available P over multiple planting cycles.
• A soil phosphorus supply potential model was developed based on soil available P and the number of planting stubbles.

Main Results:

• Soil inorganic and occluded P remained relatively stable, while other fractions like water-soluble, Al-P, Fe-P, and Ca-P showed initial decreases followed by increases.
• Soil available phosphorus exhibited a linear decline over time.
• A critical soil phosphorus deficiency threshold of 200 mg kg⁻¹ was identified for spinach cultivation.
• A predictive model (y = 6.759 + 0.027x, R = 0.99) was established relating soil available P (x) to planting stubbles (y).

Conclusions:

• Continuous spinach cultivation without P fertilization alters soil P fraction dynamics and depletes available P.
• The established model provides a tool for predicting P requirements and optimizing fertilizer application rates.
• Findings support the development of sustainable fertilization practices to reduce P pollution from protected agricultural fields.