ASABE Technical Library - Abstract

Abstract. Single superphosphate (SSP) is the most commonly used fertilizer in New Zealand. It has been the preferred fertilizer because New Zealand soils are deficient in both phosphorus and sulfur. Traditionally, perennial rye grass (Lolium perenne_cv) and white clover (Trifolium repens_cv) pastures are cultivated to provide grass fed, meat, wool and dairy products. It also encourages nitrogen fixation and provides a good source of crude protein through white clover.

SSP is produced in a continuous manufacturing process and granules form in a simple drum granulator. Particles range from fines less than 0.5mm in diameter to 7mm in diameter. Fines comprise, between 0.3% and 40% of product in sales depots. The product is brittle and is inclined to break up with handling; larger particles are stronger than smaller ones. Airplane and truck spreaders claim that they are unable to deliver SSP accurately due to variation in particle size distribution and have asked the manufacturers to granulate the product into a homogenous product with greater particle strength.

This paper examines the costs of granulation by several methods and compares the cost of a granulated SSP to alternative fertilizers which can deliver the same nutrient. It also compares the added cost of fertilizer to the benefits of improved spread, in terms of accuracy.

It concludes that fully granulated SSP is not economically viable as alternative products which can deliver the same nutrient that are already granulated would be a cheaper option. Granulating SSP would significantly reduce demand for the product.