A glasshouse evaluation of sulfur fertilizer sources for crops and pastures. II. A comparison of sulfur coated triple superphosphates and gypsum

Abstract

In many parts of the world it has become more economical to use triple superphosphate (TSP) rather than single superphosphate (SSP) as a pasture fertilizer where only P deficiency exists. Coating TSP with elemental S is an attractive alternative to SSP for situations where P and S deficiency exists. A pot experiment was conducted on an S deficient Aquic Haplustalf soil to compare the ability of gypsum (G) and S coated TSP to supply S to a ryegrass/white clover pasture over 14 repeated harvests over a 96 week period. The adhesives used to coat S to TSP were UNE1, UNE3, UNE2 and a commercial product (HF). The reverse dilution 35S technique was used to calculate fertilizer S uptake. Total yields were highest with G and UNE1. Total fertilizer S recovery by the pasture was 64.4% for G and 52.3% and 52.9% for UNEl and UNE3 respectively. These amounts were significantly higher than from UNE2 or HF. The time course of fertilizer S release varied between products and shows that bonding method can affect S availability from S coated TSP products.