Story: Soil investigation
Page 2 – 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.
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.