Superphosphate
New Zealand’s soils are by and large not naturally fertile, simply because of the low levels of some key nutrients – phosphorus (P) in particular – in the volcanic and sedimentary rocks they have been formed from. Single superphosphate (SSP), made by reacting finely ground phosphate rock with concentrated sulphuric acid, was first produced in New Zealand in 1899, and was found to totally transform production on many soils. For decades what fertiliser was used was put on by truck, or, in the cleared hills, by hand. That all changed after WW2 with the advent of airspreading (aerial topdressing). Combined with oversown grass and clover seed and subdivision, massive increases in productivity were obtained. ‘The three esses; seed, super and subdivision’ became the mantra.
Several public companies and farmer-owned cooperatives commenced manufacturing SSP from the conveniently-located, high P-content phosphate rocks from Nauru and Christmas Islands. SSP production peaked at over 3 million tonnes per year in the 1970s. The economic downturn of the 1980s and the removal of government fertiliser subsidies saw production halve, leading to takeovers and mergers. It also lead to a steady decline, which continues to this day, in the number of fixed-wing spreading aircraft and trained agricultural pilots in New Zealand. The last public company, FERNZ, sold its operations in Northland and Taranaki to Ballance (at that time called Bay of Plenty Fertiliser Cooperative or BOP) and Ravensdown respectively in the early 1990s.
New Zealand’s soils are by and large not naturally fertile, simply because of the low levels of some key nutrients in the parent materials…
Fertiliser Friction
The takeover of the sole remaining single-works SSP cooperative (Southfert) by Ballance saw the two remaining cooperatives embark on a bitter war in which they replicated each others infrastructure throughout the country. Ballance now has SSP works only in Mt. Maunganui and Bluff; Ravensdown at Ravensbourne (Dunedin) and Napier.
Hill-country fertiliser use has recovered since the 1990s, but is still well below its peak. However, the steadily increasing growth in area in dairying since the mid-1990s, especially on the previously predominantly cropping and sheep-grazed plains of Canterbury and Southland, and the intensification of production on existing dairying land in the central North Island and Taranaki, has seen massive increases in fertiliser use, particularly in the forms of granular urea, DAP and potash. Today, about 65% of all fertiliser is applied by commercial groundspreading trucks and about 20% by air, with the remainder (mainly represented by urea ) spread by farmers.
The Ballance-owned Kapuni urea plant produces 260,000 tpa, virtually all of which is sold in the North Island. Total imported urea (Ballance, Ravensdown and Fert Wholesale Direct) accounts for a further 550,000 tonnes across New zealand. Most of this is spread by truck or farmer-owned spreading equipment. The losses of N to the environment from this massive growth in urea use, both directly, and indirectly through N losses from cow urine patches, is the one of two fundamental cause of the environmental problems New Zealand faces today, the other being phosphate run-off.