CHANGES IN SOIL CHEMICAL-PROPERTIES UNDER LONG-TERM SUGAR-CANE MONOCULTURE AND THEIR POSSIBLE ROLE IN SUGAR YIELD DECLINE

Soil samples from paired 'old' and 'new' sugar cane soils from 6 contr asting sites in 3 climatically contrasting areas of North Queensland w ere analysed to identify changes in soil chemistry resulting from cont inuous sugar cane monoculture. The aim was to identify soil factors th at may be associated with, or act as triggers to, the expression of su gar yield decline. It was found that there was no consistent effect of time under sugar monoculture on soil chemical properties across all s ites, when either the distributions of properties through the soil pro file, or property values at specific depths, were considered. However, marked effects were noted at some sites with respect to some soil pro perties, and the lack of consistent results across all sites may there fore be attributable to the inherent differences between the soils sam pled. These effects were generally consistent with soil acidification.