Sustainable landuse is about the ability of soil to reproduce the current agricultural yield levels for the future generations. This allows changes in soil characteristics with the stipulation that the soil retains its ability to recover over time. This paper investigates sustainability aspects from observations at an experimental site in the Brigalow bio-region of Central Queensland, where the site was set up comprising of three blocks - one as scrubland, another as pasture, and the third for cropping. The region underwent major landscape changes due primarily to land clearing since early 1960s, but landuse for the experimental site was fully developed by 1984. Data collected since then revealed that soil quality declined over time even for the scrubland which suggests that the semi-arid environment of the region is unable to preserve soil quality without human intervention. Productivity of cropping and grazing indubitably declined accompanied by soil fertility reduction, soil erosion and soil structural degradation without remedial measures. To get insight into proper strategies for land management, a mathematical model is developed that accounts for soil moisture and fertility. The model presents scenarios and effects for different rates of fertilizer applications, different regimes of irrigation, and different strategies of land management.