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Saline soils: Why Nuclear?

The IAEA project on saline soils illustrates how the use of atoms in agriculture can help to prevent the degradation of farmlands and point the way towards more productive harvests. The project combines several proven nuclear techniques and applications to provide key pieces of information to soil scientists, farmers, land managers, and irrigation specialists.

• Neutron moisture gauges, or probes, are being used to monitor soil conditions and irrigation practices. One result is that irrigation can be better managed -- only needed amounts of irrigated water are applied and salt accumulation is better controlled.
• Chemical elements called isotopes are being used for water, soil, and plant studies. Both stable and radioactive isotopes help scientists analyze groundwater resources, providing information about the quality and quantity of groundwater recharge and thus the sustainability of its use. Other isotopes can be used for "labelling" plants to trace the pathways of elements such as carbon and nitrogen that circulate from the atmosphere to plants to soil and again into the atmosphere. (Also see, Partners in the Lab.) Their study can provide information on the effect of plants on soil structure and fertility, for example. Some isotopes, such as those of chlorine, can be used to monitor the movement of saline water, yielding valuable information to guide sustainable farming practices on saline lands.
• For water studies, isotopes of hydrogen and oxygen are of special interest. Deuterium, or hydrogen-2, and oxygen-18 are heavier and much rarer than the more abundant isotopes hydrogen-1 and oxygen-16. Tritium, or hydrogen-3, is even rarer and radioactive. Rising water vapour from oceans has a lower concentration of the heavy isotopes than seawater. This means that when it rains, the heavy isotopes rain out first, and that the precipitation changes isotopically as clouds move inland. In the process, water acquires individual and characteristic "fingerprints" in different environments. In groundwater studies, the decay of tritium dates the groundwater over decades; radiocarbon in dissolved lime can "date" many millenia. When hydrologists analyze data from water samples, they gain historical insights into the water source's dynamic lifespan, including its age, origin, and transport processes, that help shape decisions about how the water is used in the future.

Taken together, nuclear and isotopic techniques have become keys of efforts to fight the environmental degradation of arable lands. The tools are safe, precise, affordable, and sometimes the only means to study the complex interrelationships between soils, water, and plants.

Agricultural development is a central component of the IAEA's technical cooperation programme, which is placing renewed emphasis on demonstrating innovative solutions for conservation and agricultural production of marginal lands. An overriding goal is to strengthen national capabilities for implementing common policies and international protocols. Projects particularly seek to encourage and broaden technical cooperation among developing countries to tap regional expertise and resources in applying tools of nuclear science and technology to shared problems.

Through technical cooperation and related channels, the IAEA is seeking to strengthen its collaboration with international and regional organizations committed to sustainable agricultural development. A central role is played by the United Nations Secretariat of the Convention to Combat Desertification, which helps to mobilize resources to support national and international actions against land degradation. The IAEA's scientific and technological resources can contribute in key ways to overcoming the challenges ahead through stronger partnerships and well-defined cooperative programmes.