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The demand to improve soil health, arrest land degradation, in particular desertification in agro-ecosystems and protect land and water resources for food production and sustainable agricultural and socio-economic development is expected to increase in the next 50 years as a result of the continuing worldwide population growth and the increased reliance on limited natural resource-based economy. Moreover, the intensive competition for land and water resources from industrial, urban and other sectors and the impacts of widespread soil degradation and global climate change will place increasing pressure on the need to improve sustainable land and water use and management. The objective of the Soil and Water Management & Crop Nutrition (SWMCN) Subprogramme of the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture is to assist Member States to use isotopic and nuclear-based techniques to diagnose constraints and pilot-test interventions to intensify crop production in a sustainable manner through the integrated management of soil, water and nutrient resources without land degradation. This objective is pursued through a range of activities including (a) co-ordinated research projects (CRP) which involve international networks of national agricultural research organizations from developing countries, advanced research institutes and CGIAR institutions, and (b) technical co-operation projects (TCP) that promote technology transfer through technical support and institutional capacity building in FAO and IAEA Member States. This chapter will report on the application of isotopic and nuclear techniques to unravel processes and factors that affect land degradation and major findings obtained from both CRPs and TCPs that were aimed to avoid and mitigate land degradation. Since land degradation includes not only soil erosion but also the decline in soil quality and their constituents (such as water and nutrients) with its subsequent reduction in crop production, projects that are associated with improving soil health, minimizing nutrient mining, combating soil salinity, soil acidity and desertification and enhancing water use efficiency will also be briefly presented and discussed.