Struvite as a substitute for imported phosphate fertilizers

Earlier studies from North America and Europe have proven the effectiveness of struvite as a phosphorus source for plants on annual crops in neutral or alkaline soils with a pH above 6.5. In New Zealand, primary production relies on perennial pastures with mixed species in acidic soils where the pH is below 6.5. In this regard, comprehensive work was carried out, including field, laboratory, and controlled experiments with soils having different phosphorus retention capacities.

A two-year field experiment demonstrated that the application of phosphorus in the form of struvite increased the uptake of the element by perennial ryegrass by more than 30% compared to single superphosphate. This makes it possible to achieve a similar crop yield while reducing the volume of phosphorus applied to the soil by a third. Data from a three-month greenhouse experiment on two acidic pasture soils showed that plant phosphorus uptake was on average 49% higher when using struvite.

Soil analysis after field and greenhouse tests confirmed higher concentrations of potentially plant-available phosphorus when using struvite. A laboratory incubation experiment on three acidic soils also recorded a higher increase in available phosphorus 63 days after struvite application.

In addition, a controlled-environment study revealed that struvite significantly reduces immediate phosphorus losses from the soil via drainage compared to single superphosphate. The total volume of phosphorus in the leachate from the low-retention soil turned out to be 80% higher when using single superphosphate.

The results obtained confirm that wastewater-recovered struvite can serve as a viable alternative. The next stage of the work will be to assess the impact of various soil types, plants, and environmental factors on the effectiveness of struvite, as well as to analyze its commercial viability.