Two companies – Ravensdown Fertiliser and Ballance Agri-Nutrients – import roughly a quarter million tons of this phosphate each, each year. Since one of Ravensdown's main factories is at Awatoto, Napier is a common destination.
However, if the cargo is intended for Ballance works, then the listed ports make sense, as that company has factories at Mt Maunganui and Invercargill.
Regardless, it's a trade the companies – both farmer-owned co-operatives – carry on despite knowing the phosphate comes from a non-sovereign territory occupied by neighbouring Morocco, and that the mineral – and the proceeds of its sale – rightly belong to the indigenous inhabitants of the area, the Saharawi.
The thin pretext both companies give is that they have been assured by the Moroccan authorities that all profits flow back to Western Sahara. The Saharawi say otherwise.
You will still find Western Sahara marked on a map of the world. Since its Spanish colonisers withdrew in 1975 Morocco has gradually taken over, by force, most of the country except a small eastern strip they apparently cannot be bothered with – because they already hold the main asset, the areas with phosphate-bearing rock.
Ravensdown and Ballance claim they are "complying with UN guidelines" when buying the phosphate from Moroccan company OCP.
The company insists New Zealand soils need the sulphur and phosphorus contained in the superphosphate they manufacture, and there is "no current alternative source of phosphate rock".
Nothing like commercial imperative, eh?
NZ and Australia have already mined-out Nauru and Banaba in Kiribati of their phosphate, virtually destroying both islands in the process. The Bou Craa mine in Western Sahara is surrounded by 70 per cent of the world's phosphate reserves; China, with 5 per cent, has the second-most, followed by Syria, Algeria, and Russia.
Meanwhile Ravensdown boasts of running the largest "environmental consultancy" in the country, and Ballance sponsors what are perceived as the premier agricultural environmental awards – something I've always found incongruous.
Apparently superphosphate must be applied to pastures because our soils are otherwise "too poor" to support good grass growth. And perhaps that's true – for an intensively-farmed monoculture.
Regardless, isn't it about time Kiwi farmers – especially those with shares in these co-ops – stopped and asked themselves whether their chemical-dependent methods are really worth relying on the "blood sands" of the Saharawi?
And how many of the 160,000 Saharawi living in refugee camps in Algeria their purchase of "super" has kept there?
Bruce Bisset is a freelance writer and poet. Views expressed are the writer's opinion and not the newspaper's.