The use of soil analysis for predicting the response to sulphur of pasture legumes in the Australian tropics

Abstract

Sulphur extracted from soil with 0.05Ca(H2PO4)2 is shown to be useful for predicting responses to applied sulphur when establishing legumes into the native pastures of the Australian tropics. In many of the soils, levels of extractable sulphur are low (particularly in the surface horizon), and it is found that the use of a weighted profile mean gives improved predictions. A weighted profile mean of 4 ppm distinguished the responsive from the non-responsive sites. For some soils, extractable sulphur levels were much higher and increased with depth; these soils contained more than 15 ppm extractable sulphur in the surface horizon, and this criterion alone could be used to classify these soils as non-responsive. Species differences were not found. Using these criteria, 25 out of 27 observations would have been correctly predicted.