Fert Options with Robin Boom Agronomic Advisory Services

In November Ballance Agri-Nutrients launched a new phosphate fertiliser called Surephos.

Although it is not a true dicalcium phosphate fertiliser, it has DCP characteristics in that it is only slightly acidic, and has a much lower water-soluble P content of around 30 per cent compared to straight superphosphate which is 85 per cent water soluble, but it is not low enough to be classified as a genuine dicalcium phosphate product. Pure dicalcium phosphate products, such as DCP 18, has almost no water-soluble P – at less than five per cent – but is around 90 per cent citric soluble P, whereas superphosphate is 90 per cent citric soluble P and Surephos has about 70 per cent citric soluble phosphorus.

Water solubility

With a much lower water solubility its suitability is mainly for soils where phosphate is prone to leaching, with low Anion Storage Capacity (Phosphate retention) characteristics such as the raw peat soils in parts of the Waikato, the podsol soils of Northland and the East Coast, and Pakahi Sand soils of Westland. Also parts of the country with excessive phosphorus in the waterways, using a product like Surephos can have considerable merit. But is still not as good as Reactive Phosphate Rock fertilisers which have no water soluble phosphorus, but between 30-50 per cent citric soluble phosphorus, depending on the source of RPR.

Surephos is advertised as having 7.8 per cent total P, nine per cent Sulphate Sulphur, 22 per cent calcium and two per cent magnesium. And at $330/tonne it is about 15 per cent more expensive than superphosphate per kg of P. Compared to locally manufactured 50/50 lime/super based dicalcium phosphate products made by companies such as Hatuma, Avoca, Terracare and Fertco, it works out cheaper per unit of P, but not quite as cheap as some of the imported high analysis dicalcium phosphates. It should also be borne in mind that Surephos is not a genuine dicalcium phosphate. Serpentine Super made by both Ballance and Ravensdown has similar water soluble and citric soluble P characteristics to Surephos, but it has one per cent less total P and S at 6.8 per cent  and eight per cent respectively, although serpentine super has a higher magnesium level of five per cent. Soils with very high ASC (Phosphate retention) levels such as volcanic ash soils, using less acid fertilisers such as Surephos, serpentine super and dicalcium phosphate products can have some merit as the P can remain plant available longer since it is not as rapidly fixed by the aluminium in the soil compared to strongly acidic superphosphates.

Selling quick

The first boatload of Triple Plus, imported by Australian company Fert Direct Pty Ltd, is a competitively priced sulphur infused triple super which arrived via Mount Maunganui mid-December, but was all sold within three weeks of arrival. Two more boatloads are due to arrive in February. Back of the envelope calculations show Triple Plus to be 10-15 per cent cheaper than superphosphate once cartage and spreading costs have been included for hill country farms where fertiliser is flown on. It has other advantages of being fully granulated with very little dust, and logistic savings in terms of trucking and wear and tear on airstrips go, which can make this product attractive. The price advantage drops off for ground-spreading when Ballance and Ravensdown company rebates are factored in. Triple Plus has 18 per cent P and 11 per cent S with most of the sulphur in fine elemental form below 35 microns which should all work over a 12-month period, costing $610/tonne ex Waharoa. This same company also hope to import some MAP (Mono Ammonium Phosphate) into the country in April which at 10 per cent N and 22 per cent P is the highest commodity traded phosphatic fertiliser, and are hoping to sell it for around $200/tonne cheaper than what Ravensdown currently have it listed on their price list.

Competition

Competition by small companies like this one and the likes of Dickie Direct, Fert Wholesale Direct and Fertilisers Direct is good in my opinion. What has also been good to see is the drop in RPR prices by both co-ops this year, even though some of the rock components are questionable. Last year they were selling RPR blends for around $349/tonne, but currently Ravensdown are selling it for $329/tonne and Ballance for $265/tonne, which at 13 per cent total P looks a better option than superphosphate (nine per cent P) at $310/tonne. However there are things like current P status, soil pH, rainfall, citric solubility component, fine particle drift etc which need to be considered before embarking on a RPR fertiliser programme. Seeking qualified, informed advice on all of these products is important to ensure you are getting your best bang for your fertiliser spend.

Robin Boom, CPAg, member of the Institute of Professional Soil Scientists. Phone: 0274448764.