Flood frequency is known to be important for increasing floodplain soil nutrient supply and hence enhancing floodplain production. Observations in the floodplains of the Lower-Balonne catchment, SW Queensland have identified that frequently inundated areas are more productive than less frequently inundated areas and it is? thought that this may relate to nutrient supply. The aim of the project was to investigate the effects of flood frequency on floodplain soil nutrients and to examine the relationship between floodplain soil nutrients and plant growth in the Narran River floodplains, SW Queensland Australia. Soil samples were collected from frequently, infrequently and rarely inundated floodplains and were tested for bioavailable phosphorus and nitrogen. The floodplain sedge, Cyperus bifax and spring wheat, Triticum aestivum L. Gardia were grown in soils from different flood frequencies under laboratory conditions. Phosphorus and nitrogen treatments were also added to T. aestivum to test for soil nutrient limitations. The results found that the concentration of soil phosphorus and nitrogen were not significantly different for soils that experience different frequencies of inundation. Further, there was no difference in the above ground production of these two species of plants grown in soils from different flood frequencies. For fertiliser treatments, phosphorus additions had no effect on above or below ground production, and nitrogen additions significantly increased above ground production in soils of all flood frequencies. The results suggest that the observed differences in the productivity of floodplain areas experiencing a different flooding frequency can not be attributed to phosphorus and/or nitrogen supply. The soils were not limited by phosphorus supply and past flooding has been important for the formation of phosphorus rich floodplain soils. At present the deposition of more phosphorus rich sediment will not improve the fertility of the floodplain soils. On the other hand, the soils were limited by nitrogen supply and it is not known what effect the flood frequency has on nitrogen supply. It is suggested that growing crops that are capable of fixing nitrogen may alleviate nitrogen limitation. Floodplain productivity appears to be governed by the subsidies (e.g. increased water supply) and stresses (e.g. drought and waterlogged soils) invoked by an unpredictable flood regime. Changing the flooding frequency will alter the stress experienced by different vegetative communities and this will lead to a change in species composition and production within the floodplains of the Narran.