Reducing phosphorus release from paddy soils by a fly ash-gypsum mixture

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Chemistry

Background:

• Rice cultivation faces challenges with phosphorus (P) loss and boron (B) toxicity.
• Fly ash and phospho-gypsum are industrial byproducts with potential soil amendment properties.

Purpose of the Study:

• To evaluate a fly ash and phospho-gypsum mixture as a source of calcium (Ca) and silicon (Si) for rice.
• To assess the mixture's efficacy in mitigating boron toxicity and reducing phosphorus loss in paddy soils.

Main Methods:

• A 50:50 (wt:wt) mixture of fly ash and phospho-gypsum was applied at 0, 20, 40, and 60 Mg ha⁻¹.
• Experiments were conducted in two contrasting paddy soils (silt loam and loamy sand).
• Changes in soil phosphorus fractions (water-soluble P, Fe-P, Ca-P, Al-P) were analyzed during rice cultivation.

Main Results:

• The mixture significantly reduced water-soluble phosphate (W-P) by transforming it into less soluble calcium-bound P (Ca-P) and aluminum-bound P (Al-P).
• Lancaster and Mehlich 3 extractable P increased with increasing application rates.
• The mixture effectively supplied Ca and Si to the soil.

Conclusions:

• Fly ash and phospho-gypsum mixtures can effectively reduce phosphorus loss from rice paddy soils.
• This amendment strategy enhances soil fertility by increasing available P and supplying essential nutrients.
• The application of this mixture offers a sustainable approach to managing soil nutrients and reducing environmental pollution from agricultural runoff.