Opportunity cropping has been shown to reduce mean annual deep drainage compared to long fallow systems. A question that remained was the effect of added fertiliser nitrogen under each of the cropping systems and whether it would make a significant difference to amounts of deep drainage and to profitability. Estimates of crop yield and deep drainage results were generated using the APSLM (Agricultural Production Systems Simulator) cropping systems model, to compare long-fallow wheat/sorghum and two opportunity-cropping scenarios on a vertosol on the Liverpool Plains using rainfall data from 1958 to 1997. The results showed that fertiliser nitrogen did have a significant effect on deep drainage and gross margin under each cropping system. However, higher rates of nitrogen only produced small marginal benefits.