A RE-EVALUATION OF THE BASIS FOR DERIVING POTASSIUM FERTILISER RECOMMENDATIONS IN THE AUSTRALIAN SUGAR INDUSTRY

Potassium is an essential nutrient for sugarcane production. It is important to ensure that potassium fertiliser use is optimised and takes into account the wide range of conditions in the Australian sugar industry that can influence crop potassium requirement. This paper reports on an investigation aimed at determining whether evidence exists to support modification of the current K fertiliser recommendations. While the analysis of leaf samples collected from blocks of commercial cane indicated that third leaf K values differed markedly between regions within the industry, re-evaluation of data from past trials has suggested that the current critical value for soil exchangeable K could be replaced with at least two values based on soil textural groupings. The need to fine-tune fertiliser recommendations was supported by the results of a series of pot experiments conducted on a range of sugar industry soils. These indicated that responses to applied K were generally not well predicted by the current norms. In addition, it was found that soils differed markedly in their ability to release non-exchangeable K and that this K release was reflected by plant uptake of K. It is suggested that current potassium fertiliser recommendations and inputs are not adequately covering the wide range of conditions that exist within the industry and that modifications to the current system are warranted.