Predicting phosphorus availability from chemically diverse conventional and recycling fertilizers

Area of Science:

• Agricultural Science
• Environmental Chemistry
• Soil Science

Background:

• Biowaste-derived fertilizers are gaining importance due to their phosphorus-rich nature.
• Processing methods like combustion and pyrolysis create diverse physico-chemical properties in these fertilizers.
• Accurate characterization of phosphorus (P) availability is crucial for effective utilization.

Purpose of the Study:

• To evaluate different methods for assessing phosphorus availability in heterogeneous biowaste fertilizers.
• To compare standard fertilizer extraction techniques with novel methods like the iron bag and diffusive gradients in thin films (DGT).
• To determine the best predictors of plant phosphorus uptake and growth.

Main Methods:

• Tested 13 contrasting biowaste fertilizers using standard extractions (Olsen, CAL).
• Employed a continuous, sink-based P extraction method (iron bag).
• Assessed P availability in fertilized soil using Olsen, CAL, and DGT tests.

Main Results:

• Standard fertilizer extractions showed weak correlation with plant P uptake.
• The iron bag method demonstrated high correlation (R ² =0.73–0.85) with plant P uptake.
• DGT tests in soil performed comparably or better than Olsen tests, with R ² ≈0.90 for P uptake and plant growth.

Conclusions:

• Standard phosphorus fertilizer tests may not be suitable for diverse recycled biowaste materials.
• The iron bag extraction and DGT soil tests are promising alternatives for assessing P availability.
• Reassessment of current P availability testing protocols is necessary for sustainable fertilizer recycling.