With reactive phosphate rock (RPR) now an established mainstream product across New Zealand, it is important for farmers to know that all RPRs are not equal.
Twenty years of importing RPR has made it abundantly clear to Summit Quinphos that reactive phosphate rock comes in various guises with different performance attributes, warns Willie Thomson, General Manager at Summit Quinphos.
“There have been numerous trials carried out on dozens of different rocks across the world and, out of all of those trials, three key RPRs have stood out as being superior to the rest – Gafsa from Tunisia, Sechura from Peru and North Carolina from the USA.
“Throughout the world, there is no dispute among scientists that these three products are highly reactive phosphate rocks fully suitable for direct application.”
Mr Thomson warns however that farmers should think long and hard before using untested RPRs in what is becoming a growing market.
”We are increasingly concerned about claims in the marketplace promoting products as RPRs that are not recognised internationally as suitable for use in direct application – and that don’t have Fertmark registration.
“We know there is wide variation in the field performance of so-called RPRs, so farmers would be wise to ask for evidence of local trial work comparing the product with the renowned three RPRs before purchasing.
“My advice is to rely on the quality RPR products that have been properly tried and scientifically proven on New Zealand farms. That’s why Summit Quinphos sells Gafsa as its main RPR.”
Dr Jamie Blennerhassett, Commercial Manager at Summit Quinphos, says RPR is not chemically treated with concentrated sulphuric acid, unlike single superphosphate, so it has the added benefits of being organically certified and better for the environment.
“The high-density and phased release features of our phosphate (P) combine to greatly reduce run-off of phosphate into waterways compared with more soluble P forms, thereby minimising eutrophication problems,” says Dr Blennerhassett.
“RPR also avoids the excessive uptake of phosphate, and subsequent loss in excreta, by providing plant-available P on
sustained basis, matching the needs of the pasture.”
As well, each tonne of RPR has the same beneficial liming or anti-acidification effect as half a tonne of lime, reducing the need for lime application.
RPR requires acidic soil (<pH 6.1) and adequate annual rainfall (>800 mm) to be effective, so virtually all New Zealand agricultural soils permit its use.
“We also add sulphur to our RPR to meet the requirements of specific New Zealand pastures, varying the amount and sulphur particle size according to each region’s soil and climate characteristics.”
Farmers can contact Summit Quinphos field consultants on 0800 784 674 for more information about RPRs.
27 October 2010