Story: Soils and regional land use
Underlying New Zealand’s varied landscape is a mosaic of soils. The type of soil, along with temperature and rainfall, determine how the land will be used for farming. But even inhospitable land can be developed with fertiliser to make it suitable for raising animals and crops.
Full story by Allan Gillingham
Main image: Vegetation pattern in tussock grassland
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How the land is used for farming depends on its topography (contours), the type of soil it has, and the climate (especially temperature and rainfall).
About half of New Zealand’s land is used for agriculture – as pasture for grazing stock, orchards, crop or forest plantations.
The further south you go, the cooler it gets – the mean annual temperature in Auckland is 15.3°C and in Dunedin it is 10.8°C. It also gets cooler the higher you climb.
The fertility of soils varies around New Zealand, but fertilisers are used wherever plants and animals are farmed. Fertilisers balance nutrients that occur naturally in the soil to ensure plant and animal growth. The main fertiliser nutrients applied for growth are nitrogen, phosphorus and sulfur. Trace elements, needed in tiny amounts, include boron, copper, cobalt and selenium.
Flat land on the Southland and Canterbury plains, and in Central Otago, is mainly used for growing crops and increasingly for dairy farming. Some of these areas are very dry and need irrigation.
Rolling and moderately steep hills are used for sheep, beef and deer farming, and forestry. This sort of landscape makes up much of Northland and the central North Island. Northland’s soils are acidic, so pastures need to be treated with lime, as well as superphosphater fertiliser.
The undulating land of South Auckland and Waikato is some of the most fertile in the country. The soil is made up of layers of volcanic ash, making it free-draining and easy to cultivate. The rainy West Coast of the South Island is not so easy. Some soils are formed from flood gravels, and need drainage and fertiliser to be productive. Other very old soils need to be broken up with diggers, re-shaped into a giant corrugated-iron pattern and heavily fertilised to improve drainage.