Agriculture currently accounts for about 70% of global freshwater use and the Food and Agriculture Organisation (FAO) of the United Nations (UN) forecasts that, by 2050, global water requirements for agriculture will increase by 50% in order to meet the increased food demands of a growing population. With an increasing scarcity of freshwater, due to indiscriminate use and a changing climate with extreme weather events of droughts and flooding, there is an urgent need to improve the management of this resource. Isotopic and nuclear techniques are useful and effective tools to assess the soil water status, particularly in the immediate vicinity of crop roots, to trace soil water movement and to identify hot spots of land degradation that deliver sediments and affect downstream water quality. Such information assists in developing strategies for sustainable agricultural water management.
|Water scarcity in Africa|
Nuclear techniques for improved water use efficiency
Nuclear and isotopic techniques play an important and sometimes unique role in providing information essential to developing strategies aimed at improving agricultural water use efficiency, and hence in providing solutions to mitigate the increasing water scarcity.
|Soil moisture neutron probe used in agriculture|
- The soil moisture neutron probe (SMNP) is ideal for the measurement of soil water in the immediate vicinity of the crop roots, and providing accurate data on the accessibility to the crop of available water to establish optimal irrigation schedules. The SMNP is currently the most suitable instrument to accurately measure soil moisture under saline conditions. It is also widely used to calibrate conventional moisture sensors for direct use in farmers’ fields.
- Both oxygen and hydrogen are components of water. The use of the isotopic signatures of oxygen (18O) and hydrogen (2H) in water vapour taken from field crops can facilitate the quantification of crop water uptake, i.e. plant transpiration, and water lost through soil evaporation. It therefore provides information on factors affecting transpiration and evaporation, essential for improving the water use efficiency of crops.
- Carbon (C) is an important building component of plants. Green plants assimilate carbon from atmospheric carbon dioxide through the process of photosynthesis. Carbon dioxide is composed of two stable isotopes, the less abundant 13C and the lighter 12C. During photosynthesis the plant discriminates against the heavier isotope in favour of the lighter one. The extent of this discrimination depends on environmental factors, such as water availability and salts in the soil. The variation in the relative abundance of the carbon isotopes can therefore be used as a surrogate marker of water stress, water use efficiency and crop tolerance to drought and salinity.
Nuclear techniques for enhanced water quality
|Good water means Good crops!|
Traditional and recently developed isotopic techniques based on the use of stable isotopes, fallout radionuclides of caesium (Cs), lead (Pb) and beryllium (Be), and compound specific isotope analyses assist in determining agricultural activities that threaten water quality and in identifying hot spots of land degradation in agricultural landscapes.
- 15N isotope tools are used to trace the movement of applied 15N-labelled nitrogen (N) fertilisers in soils, crops and water. Information on this movement is essential to identifying factors that potentially affect nitrogen fertiliser use efficiency and water quality in agricultural landscapes in order to improve farming practices.
- Fallout radionuclides, such as caesium-137 (137Cs), lead-210 (210Pb) and beryllium-7 (7Be), assist in
- Establishing changes in soil redistribution patterns and rates in large catchment areas and in
- Evaluating the efficiency of soil conservation measures in controlling soil erosion and water quality.
- Variations in the carbon-13 stable isotope (13C) signatures in specific plant components and in soils (Compound Specific Isotope Analyses) are used to identify areas of land degradation and sources of water pollution in the agricultural landscape, and hence provide essential data to develop effective soil conservation strategies to protect water quality.
|For the continuation of resources|
~taken from IAEA factsheet on Nuclear Technology on water