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Aerial Fertilizer
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 AERIAL FERTILIZER

Eric Lee Johnson Photo
An Ecological Disaster

Julius Vogel

A Significant Remit

Ohakea Trials

Economic Viability

Institutional Support

Replacing the Tiger Moth

"The aerial distribution trials have proved that fertilizer can be dropped from aircraft successfully within the desired limits of accuracy, provided the ballistics of the fertilizer are reasonably uniform and the aeroplane has satisfactory performance under the conditions of terrain involved."

 D.A. Campbell

 New Zealand Journal of Science and Technology

Volume X 1948


An Ecological Disaster

While the development of grassland farming must be rated as a major success in terms of its ability to provide a high living standard for the population of New Zealand, in ecological terms it can be seen as a disaster. Many hundreds of square miles of forest were destroyed in the creation of the pastures without, in most cases, any use being made of the timber. In upland locations throughout the country the removal of forest cover, together with over-grazing of the tussock by sheep and by introduced animal species, particularly rabbits and deer, led to the rapid run-off of rainfall and to the occurrence of serious soil erosion. 

Julius Vogel

The serious nature of the damage being caused was highlighted many times from the 1870s on, with Julius Vogel himself urging the maintenance of the forests, but it was not until 1941 with the passing of the Soil Conservation and Rivers Control Act that effective measures to combat soil erosion were inaugurated. This Act established a soil conservation and rivers control council whose most important responsibility was the establishment and general supervision of regional catchment boards, with the main function of minimizing and preventing damage by floods and erosion. 


A Significant Remit

In 1947, after some earlier successful trials of seed distribution and then of cobalt and copper sulphate from the air by A.M. Prichard, chief pilot of the aerodrome services of the Ministry of Works, and after the Poverty Bay Catchment Board had successfully dropped willow poles onto inaccessible hill country, a remit on the aerial application of seeds and fertilisers was put to the Catchment Boards' third conference. This remit asked the Soil Conservation and Rivers Control Council to sponsor experiments in typical high hill country, where access is not easy. 

Though not initially enthusiastic, D.A. Campbell, the first chief adviser on soil conservation to the Council, investigated the proposal and recommended to the Council that it should take the responsibility for financing and organising trials.  The Council's decision to do so led to the development of one of the most important indigenous technologies to have an impact in New Zealand. 

Swift Adoption

A remarkable combination of favourable circumstances saw the technology progress from the innovation phase - its trial in prototype form - through to adoption and widespread use, in only a few years.  A major state involvement in the proving of the technology paved the way for its adoption and diffusion through the actions of a large number of individuals. 

The suggestion that aircraft be used for topdressing, made in a letter signed by Mr John Lambert of Hunterville to his Member of Parliament in 1926, is frequently cited as the starting point for the technology but the idea began to have credibility after A.M. Prichard had sowed seed from the air at Ninety Mile Beach in 1939. D. A. Campbell of the Soil Conservation and Rivers Control Council was to become one of the principal advocates of aerial topdressing, and following his recommendation to the Council, the experiments reported in the New Zealand Journal of Science and Technology took place. 

Ohakea Trials

For these trials the co-operation of the Royal New Zealand Air Force was obtained for spreading fertilizer, while seed sowing was done by the aerodrome services of the Ministry of Works.  The RNZAF fitted a Grumman Avenger torpedo bomber with a reserve petrol tank, converted to a fertilizer hopper, for the first tests. The paved area of tarmac at Ohakea was used to provide easy measurement of the intensity and spread of the dropped material. Granulated "hillside" super phosphate was dropped and a most encouraging dispersion of the falling particles, attributed to the slipstream of the aircraft, was obtained. 

Field Trials

Field trials were then organised on typical hill country near Raglan with poor access and steep slopes. The distribution of the fertilizer was again measured. From a flying point of view the trials were satisfactory but, because it contained too much fine material, the super phosphate did not flow freely in the initial run. More granular superphosphate was chosen for the third run and proved successful. 

Demonstration

In May 1949, the final steps in the advocacy phase took place when, encouraged by L.T. Daniell, a Wairarapa farmer who had advocated fertilizer distribution from the air in 1940, 125 tons of fertilizer were dropped on eleven different properties close to the Masterton aerodrome. These trials aroused a great deal of interest. The aeronautical magazine, Wings, noted the large attendance by farmers and referred to the use of the Grumman Avenger torpedo bombers as an example of turning swords into ploughshares.  Within a few months, 200 farmers had applied to have 250,000 acres treated. The adoption phase was at hand. 

Economic Viability

Before the end of 1949, private sector interests had taken over and established the technology's economic viability. Flying war surplus De Havilland Tiger Moths, with one cockpit converted to a fertilizer hopper, it was found that sorties could be flown from farm airstrips, the aircraft spending only three minutes on the ground each time around. (Most of these aircraft had been constructed at a factory at Rongotai now the site of Wellington airport.)

Flying from a strip on each farm enabled cheaper ground transport to be used to take the fertilizer to the farm.  Apart from the availability of war-surplus aircraft, an obviously favourable factor in the rapid spread of the technology at this stage was the existence of men who had learned to fly during the war and welcomed the opportunity to continue with careers in the air rather than face what might seem, in contrast, the dullness of other jobs in civilian life. 

Institutional Support

Economic conditions were favourable too. In 1950-51 a wool market "boom" developed, associated with the Korean War, and farm prices were relatively good for the rest of the fifties.  Institutional questions proved no barrier to the spread of the technology either.  The Director of Civil Aviation, E.A. Gibson, actively encouraged individuals to enter the business and was largely responsible for the passing of the 1951 Air Services Licensing Act - a measure designed to ensure stability in the industry. 

By the end of 1953 there were thirty-eight firms in the business, operating 160 aircraft, of which 146 were Tiger Moths.  In national economic terms the significant factor about aerial topdressing was, of course, the associated increase in production. By any measure 1949 was a turning point. Whether the measure is total sheep numbers, total beef cattle, or livestock units, output grew dramatically in the twenty years to 1969, with livestock units approximately doubling over the period.

Not all this increase can be ascribed to aerial topdressing but a measure of its importance can be gained from the fact that by the mid-sixties the tonnage of fertilizer spread from the air approached half of the total used. 

Replacing the Tiger Moth

The Tiger Moth was not the ideal topdressing aircraft nor did such an aircraft appear to exist. A study was made and desirable characteristics listed. These included an increased payload compared with the Tiger Moth's 600 lbs, an ability to take off and land in short distances, climbing ability and structural strength for pilot protection in the event of crashing.

A general specification was circulated to likely manufacturers but aroused little enthusiasm. However the Cable Price Corporation backed the design and manufacture of two prototypes by the American Fletcher Aviation Corporation, with the New Zealand Meat Producers Board acting as financial guarantor.  The second of the prototypes was flight-tested in New Zealand and received type approval in May 1955.

Over the next eleven years 150 FU24s, each with a payload of 1600 lbs, were assembled in New Zealand from imported components: the project was then brought to New Zealand and the aircraft built here. Improved versions have been designed, including turboprop versions. These aircraft dominate the list of those licensed to do aerial topdressing work. 

The detailed history of the technology is well covered in a number of accounts. The most comprehensive is "The Topdressers" by Janic Geelen, published by NZ Aviation Press, P.O. Box 50, Te Awamutu, New Zealand.