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Soil investigation

by  P. J. Tonkin

When a mysterious sickness caused the death of sheep and cattle in the central North Island, farmers were worried. But soil analysis revealed the cause – a lack of cobalt in soil derived from volcanic ash. The secrets of the soil have been unlocked by surveys, crucial for realising the potential of the land.


First observations

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.


Early investigations and bush sickness: 1900–1930

Experiments in soil surveying

As farming got under way, scientific expertise was needed to direct the use of fertiliser, especially on less productive land. Bernard Aston joined the Department of Agriculture in 1900, and undertook systematic study of New Zealand soils. He devised a standard set of tests for identifying nutrients available in the soil, and undertook nationwide soil fertility experiments.

The US Department of Agriculture set up a national soil survey in 1899, and their first soil maps were published by 1911. Local surveys in New Zealand, largely experimental but based on overseas experience, were made by Leonard Wild, Hartley Ferrar and Bernard Aston. Ferrar, who had been involved with soil surveys in Egypt, made detailed maps in Northland and Central Otago using US methods of classification. He and Aston were the first to adopt soil types as a basic mapping unit – similar soil types were grouped into series, and at the highest level into provinces.

Wild about soils

In 1919, while teaching at Lincoln College, Leonard Wild published Soils and manures of New Zealand. This widely used textbook, found in many farmhouses, was reprinted and updated several times over the next 40 years.

Influence of Theodore Rigg

Theodore Rigg, appointed agriculturalist at the Cawthron Institute (Nelson) in 1920, brought academic experience from the UK and US, and had a major influence on soil science in New Zealand for the next 30 years. He introduced the hand auger to extract soil samples. With J. A. Bruce he surveyed Waimea county, producing one of the first detailed soil maps in New Zealand.

Rigg attended the First International Soil Science Congress in Washington DC in 1927, returning with new insights into soil classification based on climate, geology, texture and chemical composition. He believed that the whole soil profile should be examined and recorded to the depth of the parent rock, rather than just the organic-rich surface layer. In his report on the congress, Rigg described the Russian idea of soil zonality, which had a major influence on New Zealand soil scientists in the 1930s and 1940s.

An organisational framework

Government science was reorganised in 1926. Ernest Marsden became secretary to the Department of Scientific and Industrial Research (DSIR), which merged the Geological Survey and Dominion Laboratory. Recognising the importance of agriculture to the New Zealand economy, Marsden set up a small soil survey group within the Geological Survey. Rigg was a member of the DSIR council from 1926 to 1954, and promoted cooperation between the Cawthron Institute and DSIR soil scientists.

Aston’s laboratory remained with the Department of Agriculture, setting the scene for many years of organisational rivalry.

Bush sickness

A wasting illness that affected sheep and cattle in the central North Island was given the name bush sickness, and was one of the most mystifying agricultural problems in the first part of the 20th century. It was originally identified as a form of iron deficiency by Aston in 1912, but it took more than 20 years for the exact cause to be identified. This was the catalyst for studies of the links between soils and animal metabolism.

Competing for a cure

There was some rivalry in the search for a cure for bush sickness. Elsa Kidson (Cawthron Institute) and K. J. McNaught (Department of Agriculture) each developed essentially the same methods for finding trace amounts of cobalt. They published a series of papers on cobalt levels in rocks, soils and pastures, while pointing out each other’s errors.

Les Grange and Norman Taylor had studied volcanic ash deposits (now called tephra) and had shown that bush sickness only occurred where tephras had been deposited during the Taupō and Kaharoa eruptions (about 200 AD and 1314 AD). Chemical analyses revealed that the sickness was caused by a deficiency in the trace element cobalt. Once identified it was readily cured by adding tiny amounts of cobalt to fertiliser. The success of the surveys and soil fertility experiments meant that abandoned farms could become productive.


DSIR soil science: 1930–1950

DSIR Soil Survey

In 1933 a Soil Survey Division was set up within the Department of Scientific and Industrial Research (DSIR), led by Les Grange. After a reconnaissance soil map of western Taranaki, Grange, with Norman Taylor and Charles Sutherland, began a survey of Waipā County. This established a format and set the standard for subsequent detailed surveys in Northland and Hawke’s Bay. The local names of the Waikato soils became widely accepted by farmers and researchers.

In 1936 the Soil Survey Division became a separate branch of the DSIR, under Les Grange. The growing group of soil scientists undertook surveys to assist agriculture or horticulture in regions such as Kerikeri, Whāngārei and Hawke’s Bay.

Wartime surveys

Although there had been a number of detailed surveys by the outbreak of the Second World War in 1939, there were still large areas that had not been studied. In 1940–41 almost all the resources of the Soil Survey Division were used for an emergency project to produce a survey of North Island soils at a scale of 4 inches to one mile (about 1:250,000). Soils were mapped as sets, defined by similar profiles. The maps were available by 1942, and were used to set priorities for agriculture and horticulture, and the use of scarce fertiliser.

A number of other surveys identified agricultural areas for strategic purposes – for example, to find suitable sites for military airfields and flax production.

DSIR Soil Bureau

In 1946 the Soil Survey Division became the DSIR Soil Bureau, with four groups: survey, chemistry, physics and biology. An influx of young graduates and trainees increased research in the field and in the laboratory.

Types of survey

By this time, there were three types of survey:

  • general (mapping in soil sets; scale about 1:250,000)
  • district (mapping in soil types; scale about 1:125,000)
  • detailed (soils mapped in relation to farm boundaries; scale about 1:35,000).

Classification

Norman Taylor developed the widely used genetic classification of New Zealand soils, based on processes. It highlighted the weathering of soils and climatic factors, and emphasised that soils developed in sequences (known as a soil suite). Based on factors that affected plant growth, the system brought order, and was used for many years by farmers, soil scientists and others in primary industries. In 1948 the classification was used as the legend for the first national soil map, at a scale of 1:2 million.

A stone in the soil

After fighting on the Somme battlefield in 1917, Les Grange met sex hygiene campaigner Ettie Rout while on leave in Paris. She cared for him while he was ill. Over 30 years later, while undertaking a soil survey in the Cook Islands, Grange discovered that she had been buried in an obscure grave in Rarotonga. He arranged for a new headstone – the closest that Rout came to having a memorial for her war services.

Debate about soil erosion

In the late 1930s and early 1940s there was growing concern about soil erosion on land cleared for farming. The government ordered a commission of enquiry and then passed the Soil Conservation and Rivers Control Act 1941. To put the study of erosion on a sound footing, Grange set up studies of erosion-prone areas, including the high country of the South Island and the southern part of the North Island.

But there was controversy over the extent and significance of erosion. A royal commission on sheep farming denounced the DSIR report on the high country as anti-farming propaganda. After 1948, the DSIR’s study of erosion was halted. This decision had unfortunate consequences for many years, because engineering works went ahead without the support of soil erosion research.


Golden age of soil survey: 1951–1985

Major surveys

After the Second World War, surveys were made as a result of requests from local authorities, agricultural groups, and the need to understand soils in places where there was little information. There were major investigations in:

  • Gisborne plains – later used to plan intensive horticulture
  • Rotorua–Taupō region – for planning farms and forestry
  • Fruit-growing areas of Central Otago
  • Manawatū sand country.

There was often a gap of a decade or more between a survey and the publication of maps and a descriptive monograph. This delay prevented the rapid acceptance and use of new information.

The first manual

Soil survey method by Norman Taylor and Ivan Pohlen was published in 1962. A distillation of 30 years’ knowledge, it was the first comprehensive New Zealand soil survey manual. It set standards for soil description and mapping, and included the first published version of the New Zealand genetic soil classification.

In 1962 the DSIR Soil Bureau moved to Taitā, in the Hutt Valley. It was a productive research centre, although its isolation and lack of contact with agricultural groups ultimately led to its closure 30 years later.

Competing surveys

By the late 1960s the demand for soil surveys outstripped the resources available, and there was overlap and competition between organisations. The Lands and Survey Department started its own series of 1:63,360 (1 inch to the mile) soil maps of counties based on Soil Bureau mapping. The National Soils and Water Conservation Authority undertook a national land resource survey, also at 1:63,360 scale, with soil information.

A 1980 DSIR discussion paper, Land alone endures, addressed the role of research in effective land use, and the problem of sharing information between government agencies. Widely distributed, it helped to draw attention to the loss of highly productive soils near urban areas, as well as the lack of research behind decisions about land use.

The role of universities

Canterbury Agricultural College (later Lincoln College, then Lincoln University) was the first university organisation to teach soil science, starting with Leonard Wild in 1915. More emphasis was given to soil survey after Tom Walker became foundation professor of soil science in 1952.

Massey Agricultural College (later Massey University) started teaching soil science in 1937, and Abe Hudson was made the first professor of soils and field husbandry in 1951. Long-term field trials led to the setting up of the Fertiliser and Lime Research Unit. Soil science papers have also been taught at Waikato and Victoria universities since the 1960s.

Stopping erosion

In the 1970s there was a plan to clear-fell beech forest on the West Coast and plant pine trees. Research by the Forest Research Institute and Soil Bureau showed that some areas would erode once the forest was gone. The picture of bare, worn-away hills convinced many that the scheme should not go ahead.

A team approach

One strategy for quicker soil surveys was to use large numbers of staff for concentrated fieldwork. For example, Soil Bureau teams, sometimes using helicopters, surveyed large areas on the West Coast for potential farming and forestry. Similar team surveys were made on Stewart Island, and in the upper Waitaki valley, King Country and Manukau City.

Backhoes and portable drilling rigs began to replace traditional excavation with spade and auger drill.


Changing role of soil science: 1986 onwards

Disbanding and decline

Major government restructuring in the late 1980s and early 1990s had an impact on soil investigations, especially because of the perceived duplication between different organisations. From 1987 the soil survey programme in the DSIR Soil Bureau was run down, and new soil maps and monographs were withheld from publication under a user-pays policy.

The break-up of the Ministry of Works (including the National Soils and Water Conservation Authority), Lands and Survey Department and NZ Forest Service led to many redundancies. Part of the remaining soil survey and conservation service moved to Crown research institutes that were formed in 1992, especially Landcare Research. But this has failed to resolve the fragmentation of soil science research, and funding continues to decline.

A long-term effect was a sharp decline in the number of postgraduate students of soil science, because of the perceived decline in job opportunities.

Wider scope

Soil surveying has expanded since the 1980s from mapping soils to include activities such as modelling the flow of nutrients through a landscape, identifying catchments prone to pollution, disposing of effluent, and sampling of contaminants such as cadmium and organochlorines.

The national carbon inventory began by collating all chemical data recorded in soil surveys from the 1960s to the 1980s, and now includes all data on carbon in New Zealand soils and vegetation.

The New Zealand Soil Classification

By the late 1970s the New Zealand genetic soil classification developed by Norman Taylor was outdated. Some soil classes were difficult to identify. A revised and updated version, the New Zealand Soil Classification, appeared in the 1980s, and is now widely used. It is based on orders, groups, subgroups and soil forms.

Do it yourself

A 1998 pilot project by AgResearch and Massey University staff looked at whether farmers could make their own soil maps. After a year of study, nine farmers from the Dannevirke area produced maps of their own properties. This meant they could understand soil variation on their own land, and improve farm management.

Revival in the south

A 1998–2001 survey of the soils of Southland (called Topoclimate South), initiated by the regional and district councils, aimed to find crops that might be grown in Southland. This involved monitoring the microclimate and producing soil maps, to make information easily available to farmers.

It spurred the Otago Regional Council into starting a similar project called growOTAGO, which produced a comprehensive set of soil maps. Much of the information is on the internet, and can be updated.

Soil maps in the 21st century

The national S-map programme, begun in 2004 by Landcare Research, builds on Topoclimate South and growOTAGO. All data is held digitally in the Geographic Information System. Different combinations of map data, including soils, climate and topography can be incorporated, and users can create and print maps at different scales for specific areas.


External links and sources

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How to cite this page: P. J. Tonkin, 'Soil investigation', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/soil-investigation/print (accessed 24 August 2019)

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