What is fertiliser?
Fertiliser is spread onto soil to help crops, pasture and other plants grow. Natural fertiliser comes from animal manure or decomposed plant material such as compost. Manufactured fertiliser is sold as a sand-like mixture, or in granules.
Most soils contain some nutrients that help plants to grow. But extra nutrients are needed for fast-growing, healthy farm crops or pasture (which sheep and cattle graze on). Fertilisers are an easy and effective way to enrich the soil. They contain important elements such as phosphorus, nitrogen and potassium.
In early times, farmers added compost, manure, dried animal blood and bone, and ground-up rock. These contain fewer nutrients than fertiliser.
Fertiliser industry: beginnings
Pioneer farmers planted crops, but these began to fail. A lack of phosphorus was the main problem.
One source of phosphorus is guano – accumulated bird droppings. Over a long time, these harden into a substance called rock phosphate. In 1867, the first shipment of rock phosphate was sent to New Zealand from Nauru Island in the Pacific. From 1882, companies such as Kempthorne, Prosser in Dunedin were processing it into superphosphate, a much better fertiliser for farms around the country. The fertiliser industry boomed.
Types of fertiliser
Superphosphate is made from rock phosphate. It is the main fertiliser used on New Zealand soils. Without it, sheep and dairy farming would not have thrived.
By 2003 only 55% of fertilisers were superphosphate. Increasingly, farmers are using fertilisers that contain nitrogen – the most common being urea, made in pellets or granules.
The industry today
The fertiliser industry is part of New Zealand’s biggest economic sectors: agriculture and forestry. In 2007 there were three main businesses making or importing fertiliser:
- Ballance Agri-Nutrients, owned and operated by farmers. Superphosphate is made at Whāngārei, Mt Maunganui and Invercargill.
- Ravensdown Fertiliser, also run by farmers. It has works in Napier, Christchurch and Dunedin.
- Summit Quinphos, an Auckland-based importer.
Ballance and Ravensdown import rock phosphate from North Africa, and supply 94% of the New Zealand market. In the 2000s, annual sales of fertiliser were worth $1 billion.
Fertiliser and the environment
Superphosphate contains artificial chemicals, and organic farmers do not use it. Alternative products include a rock phosphate that can be put straight onto pasture, without the need for chemical processing.
FertResearch is an organisation which provides rules, advice and research, to ensure fertiliser is used properly. If fertiliser or nutrients from farmland enter streams or lakes, they may cause weed growth or have other harmful effects.