Aerial topdressing

Aerial topdressing is the aerial application of fertilisers over farmland using agricultural aircraft. It was developed in New Zealand in the 1940s and rapidly adopted elsewhere in the 1950s.

The first known aerial application of agricultural materials was by John Chaytor, who spread seed over a swamped valley floor in Wairoa, New Zealand, in 1906 using a hot air balloon with mobile tethers.

The first known use of a heavier-than-air machine in aerial application on 3 August 1921 when as the result of advocacy by Dr Coad, a USAAC Curtiss JN4 Jenny piloted by John A. Macready was used to spread lead arsenate to kill catalpa sphinx caterpillars near Troy, Ohio in the United States. The first commercial operations were attempted in the US in 1924 and use of insecticide and fungicide for crop dusting slowly spread in the Americas and, to a lesser extent, other nations. Crop dusting poisons enjoyed a boom in the US and Europe after World War II until the environmental impact of widespread use was recognised following the publication of Rachel Carson's Silent Spring in 1963. Crop dusting was not adopted in New Zealand until after top dressing was well established.

Initial interest in New Zealand concentrated on seed sowing, but much of New Zealand's central North Island farmland, given to returned servicemen after World War I, had proven deficient in trace minerals such as cobalt, copper and selenium, forcing difficult topdressing by hand in rough country, or abandoning the land for forestry. The possibility of using aircraft was soon investigated.

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