The FAO/IAEA Soil and Water Management and Crop Nutrition (SWMCN) Sub-Program main activity is to develop and apply nuclear-based techniques in improving the integrated management of soil, water, nutrient and cropping practices, for increased agricultural systems productivity and sustainability. We assist Member States to use isotopes and nuclear techniques to diagnose constraints and pilot test interventions to intensify crop production in a sustainable manner. Our research outputs and methodologies developed are transferred to Member States within the framework of IAEA's Technical cooperation projects and through laboratory/field-based training courses and fellowships. Previous projects conducted by the SWMCN Sub-program were mainly focused on the optimization, of fertilizer recovery efficiency by cereal crops and biological nitrogen fixation in various legumes, using stable isotope 15N. The methodologies for measuring these processes are now well established in Member States with a number of IAEA Technical Cooperation projects implemented. The current challenges of the SWMCN Sub-program are to apply existing nuclear techniques and develop new applications to address water and soil conservation issues at both field and watershed levels. Recent projects have emphasized the use of nuclear techniques such as neutron probes or stable isotopes such as 18O and 13C to improve water use efficiency and water management for sustainable agricultural production in developing countries and fallout 137Cs, 210Pb and 7Be to estimate losses of soil and associated pollutants and help identify efficient conservation measures to minimize these losses. To meet these challenges a series of new Coordinated Research and Technical Cooperation Projects have been recently initiated. In these projects, integrated soil-water-plant practices that influence soil erosion, water conservation and nutrient losses are studied so that management tools can be put in place to minimize soil erosion and to optimize water and nutrient uptake. This effort has also included projects to evaluate crop germplasm for tolerance to abiotic stress such as drought and salinity, and for improving nutrient use efficiency. Case studies involving the use of nuclear techniques and isotopic tracers of past and present projects and research findings will be presented and discussed.