ALTERNATIVE PHOSPHATIC FERTILISERS FOR HILL COUNTRY

Abstract

The role of alternative phosphorus sources to single superphosphate as a maintenance fertiliser for hill country was evaluated in five experiments between 1986 1982. The experiments were located at Gisborne, Rotorua and Te Kuiti. Reactive rock phosphate-sulphur granules (previously known as biosuper) were as effective as superphosphate in the year of application, but the reactive rock phosphates applied alone were as effective on only two of the sites. Superphosphate/reactive rock mixtures were less effective than superphosphate. While most fertilisers had substantial residual effects in the second year after application there was no clear pattern between materials. When taken over two years, a single biennial application of all fertilisers was at least as effective as two annual dressings at half the rate. The role of alternative phosphorus fertilisers is discussed in terms of their cost and agronomic effectiveness, the requirements for other elements,and the structure of the present fertiliser industry. Keywords: superphosphate, phosphorus, phosphatic fertilisers, biosuper, hill country, Sechura, North Carolina, Jordan.