Two Australian Centre for International Agricultural Research (ACIAR) projects in the mid-1980s (Projects 8328 and 8804) funded research at the University of New England to help better understand and improve phosphorus and sulfur management in tropical agricultural systems. As tropical agriculture expands into more marginal land and production systems intensify, the demands for soil phosphorus and sulfur increase. Major outcomes of the research were a better understanding of the nutrient dynamics in South-East Asia and the development of a new and more reliable soil test for available sulfur. The new test (KCl-40) more accurately measured the sulfur available to plants, as it was able to measure the sulfur held within organic matter. A spin-off from the development of the KCl-40 test was its application to Australian agriculture, specifically the pasture-based livestock industries and the canola industry. This economic evaluation focuses on the impact of the project outcomes for the canola industry. Sulfur is critical for high canola yields and most New South Wales (NSW) and Western Australian soils are deficient in sulfur (less so Victoria). Even small rates of sulfur application can lift canola yields significantly, for example by 40 per cent. This was being demonstrated in field trials in the early 1990s and it quickly became standard practice for growers to apply sulfur. The use of KCl-40 in NSW research in the 1992–93 helped researchers to further demonstrate to growers the gains from sulfur and the appropriate rates to apply. While most growers had already begun to increase sulfur use, a small proportion of growers had not done so. It is this group which the University of New England research, through assisting work by the NSW Agriculture/Incitec, benefited. The value of the production increase resulting from additional growers applying sulfur is estimated to have resulted in a benefit–cost return on the ACIAR research cost of around 3.4:1 on the estimated share of the ACIAR investment which could be attributed to canola. From an aggregate perspective, these benefits paid for about half of ACIAR’s total research investment in the two projects. The KCl-40 test is now a routine component of soil tests conducted for growers in NSW, Victoria, South Australia and Western Australia, although its significance as far as influencing canola growers' decisions in respect of sulfur appears limited since the economic payoffs to using sulfur have led growers to routinely apply it. For pastures, the economics of fertiliser application depend critically upon expected response in individual situations and hence there is a demand for accurate soil tests. The KCl-40 test now means that sheep and cattle graziers and dairy farmers can rely on soil tests for sulfur to help make much better decisions.