The fertiliser industry is one of a number of service industries that underpin the largest sector of the New Zealand economy – agriculture and forestry. Nearly 14 million hectares of the total New Zealand land area (26.7 million hectares) is used for pastoral agriculture, arable and fodder cropping, or production forestry. The greatest area of arable land is under grazed, permanent pasture.
From early days, the fertiliser industry provided mostly superphosphate (made in New Zealand) and potash (potassium chloride) imported from France, Germany or Canada, for use on pasture.
Clover for nitrogen
The nutrients in superphosphate are phosphorus, sulfur and calcium. These promote vigorous growth of clover, which is one of the species that grows well in New Zealand pasture.
Nitrogen, another important nutrient, is lacking in superphosphate – but is provided by clover in a special way. Rhizobium bacteria form nodules on clover plant roots and convert nitrogen in the soil atmosphere into a form available for grass growth. This is a very inexpensive means of providing nitrogen for pasture growth.
Urea fertiliser for nitrogen
Since the early 1990s, farming costs and the value of land assets have increased much more rapidly than income from the sale of produce. Farmers have had to produce much more from their land. Backed by research trials, they have found that, compared to clover, man-made nitrogen fertiliser could produce more pasture at critical times of the year.
The main nitrogen fertiliser is urea, which contains 46% nitrogen. Its use has greatly increased since the 1990s, particularly on dairy farms.
In 1982, New Zealand’s only ammonia urea plant was built at Kapuni in South Taranaki. The fertiliser is made from natural gas from the offshore Māui gas field. The plant was part of Prime Minister Robert Muldoon’s ‘Think Big’ policy of industrial development.
Initially run by Petrochem, in 1992 it was sold to the Bay of Plenty Fertiliser Co-operative (now Ballance Agri-Nutrients). In 2008, they manufactured 260,000 tonnes of urea fertiliser annually, some of which was used in non-agricultural industries. At least that amount is also imported by the fertiliser cooperatives.
Rising from the dead
The observation in England that plants grew well in church graveyards led to the early use of ground-up bones as a phosphorus fertiliser. The bones were collected from the ancient battlefields of Britain and Europe.
In 1979, superphosphate dominated the market. But by 2003, this had declined and use of urea and diammonium phosphate had surged, while potash sales remained static. Responding to changing demand from farmers and growers, the industry produces or imports a much greater range and quantity of multi-nutrient products today.
Many niche businesses make, import or sell alternative fertilisers. These are derived from raw materials such as crushed rock phosphate, marine clay, micro-organism preparations, worm compost and other waste materials or by-products. The value of these materials should be judged on their chemical content.