Multifunctional Tailoring of Fertilizer Composites Directly Derived From Phosphate Rock

Area of Science:

• Agricultural Science
• Materials Science
• Environmental Science

Background:

• Depleting high-grade phosphate reserves necessitate alternative sources.
• Low-grade phosphate rock (LPR) contains valuable calcium (Ca) and magnesium (Mg) but is underutilized.
• Conventional NPK fertilization can lead to soil acidity and nutrient deficits.

Purpose of the Study:

• To develop a novel activation system for LPR to create multifunctional fertilizer composites (MFCs).
• To enhance the utilization of phosphorus (P), Ca, and Mg from LPR.
• To evaluate the MFCs' performance in terms of nutrient release, crop yield, and environmental impact.

Main Methods:

• A phosphorus-sulfur mixed acid with urea (PSU) activation system was employed for LPR.
• Characterization of MFCs using particle size analysis, SEM, and nitrogen adsorption-desorption isotherms.
• Pot experiments were conducted using Chinese cabbage to assess biomass increase.

Main Results:

• Optimized activation achieved 78.5%-98.3% efficiency for P, Ca, and Mg.
• Activated MFCs exhibited porous structures and enhanced nutrient adsorption capacity.
• MFCs demonstrated superior slow-release properties, reducing Ca and Mg leaching significantly (27.6% and 73.9%).
• Chinese cabbage biomass increased by 11.5%-23.4% compared to conventional fertilizers.
• MFCs proved environmentally friendly, with no heavy metal contamination risk.

Conclusions:

• The PSU activation system effectively converts LPR into MFCs with improved nutrient availability and slow-release characteristics.
• MFCs offer a sustainable solution for integrated nutrient management, addressing soil acidity and nutrient deficits.
• This approach minimizes industrial phosphorus by-product discharge and enhances resource utilization.