The Rescue of Real Reactive Phosphate Rock (RPR)
Why has Quin Environmentals offered its Algerian RPR - internationally recognised as one of the best - in 2 forms since 2018? Simply because the 'standard' RPR contains about 7% dolomite. This gives it an artificially low result in the 1970s-vintage Fertmark 30-min citsol test, because the dolomite preferentially consumes the citric acid. It does not affect its field performance. All other countries use better tests, all of which Algerian RPR passes.
But for kiwi farmers who attach any importance at all to the Fertmark test, we offer the 'V2' version. This has simply had the coarser dolomite screened out to increase the citsol, so you don't get a 'false negative'. After 2 years and 10,000 tonnes of RPR sales, no farmer has ever requested V2 ; they prefer to get a bit more Mg.
As well as false negatives, the Fertmark tests gives 'false positives' to mixes of one particular RPR (the high-cadmium Sechura) with up to 70% of non-RPRs and phosphate wastes. No other country uses tests and protocols that allow this sort of deception. The Fertmark Code has also dropped the requirement for the solubility of superphosphate to be advertised.
Time methinks for a whole new approach to Fertiliser Quality Certification. Agree?