Bio-based polyurethane coatings for controlled-release phosphorus fertilizers: Synthesis, characterization and effect...

Area of Science:

• Agricultural Science
• Materials Science
• Environmental Science

Background:

• Petroleum-based coatings in controlled-release fertilizers (CRFs) pose environmental risks.
• The efficacy of CRFs in improving phosphorus (P) use efficiency remains uncertain.

Purpose of the Study:

• To synthesize bio-based polyurethane (PU) coatings from castor oil and wheat stover.
• To evaluate the impact of these bio-based CRFs on P use efficiency.

Main Methods:

• Castor oil and liquefied wheat stover were used to create PU coatings.
• Coated monoammonium phosphate (MAP) with varying longevities (7, 37, 209 days) were tested in incubation and pot trials across different soil types.

Main Results:

• Castor oil-based PU achieved a 209-day P release longevity at a 6% coating rate.
• 37-day longevity MAP reduced P fixation and increased wheat P uptake by 50% in a high-fixing Oxisol.
• CRFs showed limited benefits in soils with lower P-fixing capacities.

Conclusions:

• Bio-based CRFs with appropriate release rates can improve P fertilizer efficiency in highly P-fixing soils.
• The effectiveness of CRFs is soil-dependent, with minimal impact expected in most soil types.