The importance of fertiliser
Farmers, horticulturists and foresters all want their pastures, crops or trees to grow as fast as possible so that their business will be profitable. On most soils, fertilisers of various types are needed to improve plant growth rates.
Without an efficient fertiliser-spreading industry, New Zealand’s farming economy could not remain viable. This is especially so for hill-country farms, which rely on fertiliser being applied from the air (aerial topdressing).
Forms of fertiliser
Nutrients can be supplied by organic manure – the waste and residue of plant and animal life. The most common method is directly applying animal dung as a solid or slurry. It can also be applied in a liquid form. The nutrient content of natural manure varies widely.
Manufactured solid fertilisers usually have specific, relatively high, nutrient contents. These fertilisers are more efficient to transport and apply than other forms. In New Zealand the most widely used fertiliser is superphosphate. It is made from imported rock phosphate that is treated with sulfuric acid to produce a white, granulated powder.
Fertiliser spreading today
In New Zealand over 2 million tonnes of fertiliser are applied annually to pastures, crops and forests by truck or tractor, or by fixed-wing or helicopter aircraft. About 40% is spread by aircraft onto steep hill-country pastures and production forestry land – the highest proportion in the world. Whereas most hill pastures receive fertiliser every one to three years, forests may be topdressed only at 10-year intervals.