Kōrero: Soil investigation

Whārangi 1. First observations

Ngā whakaahua

Gardeners from the Pacific

When the Polynesian ancestors of Māori migrated from tropical Oceania to temperate New Zealand, their gardeners looked for soils suited to growing kūmara (sweet potato), taro, yams, and gourds. In the north they found familiar reddish-brown earth, formed on weathered volcanic rocks. Fertile and well-drained soils on flat and rolling country were of great importance.

Māori developed considerable knowledge of soil types, and named them according to colour, texture, fertility, ease of cultivation and how well they drained. For example, tuatara wawata was fertile, crumbly brown soil suitable for growing kūmara; onekura was poor, reddish soil; and onekopuru was wet soil.

Sometimes they mixed the soil with sand and gravel to make it crumbly and improve heat retention – critical for growing subtropical crops in a cooler climate. These are called plaggen soils, and are found where there were stable Māori settlements, especially in the Waikato region.

The early colonial period

European explorers and missionaries recorded their impressions of soils used for cultivation, and by 1840 these were included in information for prospective colonists. Ernst Dieffenbach noted the geological origin of some soils in several areas, including the Chatham Islands. It was widely believed that the country’s lush native forests were a sign of fertile land. However, only some plants, such as pūriri trees, indicated good soil.

Settlers noticed that soil fertility varied in different parts of the country. The most productive land – for example, the volcanic soils of South Auckland – became highly prized.

Soil chemistry

In the 1840s British and European scientists began to use laboratory analysis to identify fertile soils. In New Zealand William Skey, the first government analyst, offered this service for free. In 1868 he published his findings on 33 soils, listing texture, constituents soluble in water, and material taken using hydrochloric acid. This first chemical survey formed part of a study of the suitability of lands for European settlement.

On the basis of his analyses, Skey believed that New Zealand soils had high levels of plant nutrients. Later work, however, showed that some elements could not be readily absorbed by plants.

Me pēnei te tohu i te whārangi:

P. J. Tonkin, 'Soil investigation - First observations', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/mi/soil-investigation/page-1 (accessed 14 November 2019)

Story by P. J. Tonkin, published 24 Sep 2007