Salinization – the increasing amount of salt content in soil – contributes to land degradation, desertification and subsequently food insecurity. In the Middle East, the main constraint on agricultural development of arid and semi-arid land is limited water availability, making agricultural production difficult. To address the dual challenge of soil salinity and water shortage, the IAEA, in partnership with the Food and Agriculture Organization of the United Nations (FAO), has supported ten countries in the region facing severe salinization to improve soil, water and crop management practices with the use of nuclear and isotopic techniques. Five years on, farmers are successfully growing crops under saline conditions with significant yield. Guidelines are now available to help countries produce various crops on different types of salt-affected soils.
Through its technical cooperation programme, and in partnership with the FAO, the IAEA trained and worked with 60 scientists from Iraq, Jordan, Kuwait, Lebanon, Oman, Qatar, Saudi Arabia, Syria, the United Arab Emirates and Yemen, who are now using nuclear and isotopic techniques to improve crop yields on salt-affected soils. These countries make up the Cooperative Agreement for Arab States in Asia for Research, Development and Training related to Nuclear Science and Technology (ARASIA).
“Soil salinity is dynamic and spreading globally in over 100 countries, and no continent is completely free from it,” said Mohammad Zaman, Soil scientist and Plant nutritionist at the Joint FAO/IAEA Division of Nuclear Techniques in Food and Agriculture. “However, most Middle East countries are facing severe salinization, and this is projected to increase due to climate change and its consequences: sea level rise and rising air temperature. The major challenges under these conditions are the availability of essential nutrients, especially nitrogen, as well as water for the plants that are adversely affected by excessive salts in the soil.”
Let it grow
Since the start of the project in 2014, 60 scientists have been trained in a range of nuclear and isotopic techniques, which play a key role in determining the amount of nitrogen and water required by plants. These included the use of soil moisture neutron probes to monitor soil moisture levels, and the nitrogen-15 isotopic technique which uses stable isotopes to help track how effectively crops are responding to, and taking up, fertilizer (see Soil moisture neutron probe and the nitrogen-15 isotopic technique). The information generated from these techniques allows farmers to know the appropriate type and amount of fertilizer and water required based on both the soil properties and the crop types.
With the application of the right kind of irrigation water, the physical and chemical conditions of the soil can be improved over time, as the accumulated salt is washed off, enabling a wider range of crops to germinate and grow. As a result, farmers in participating countries have managed to successfully grow different crops and achieve high production volumes. Examples include millet in Lebanon, barley and safflower in Jordan and quinoa in the United Arab Emirates.
Irrigation with saline groundwater
Soil salinization in Iraq is caused primarily by poor irrigation practices such as the use of saline water and soil compaction, leading to low drainage. According to the FAO, it is estimated that Iraq loses about 25 000 hectares per year of agricultural cropping land as a result of salinity.
With support from the IAEA and the FAO, plant biomass produced from growing salt-tolerant crops was used as animal feed. The amount of area under cultivation has increased, as farmers reclaimed saline land – which they now had the techniques to farm. “Hundreds of farmers have now returned to their land from northern to southern Baghdad,” said Ibrahim Bakri Adbulrazzaq, former Director General of the Agricultural Research Directorate of the Ministry of Science and Technology, who led the project in Iraq.
In Syria, scarcity of fresh water, deteriorating water quality and soil salinity are the major limiting factors for agricultural productivity and the sustainability of natural resources. “Results generated through the project were highly valuable,” said Mussadak Janat, researcher at the Atomic Energy Commission of Syria who led the project. “Within three years, the average okra yield became more than 13 tons per hectare, - comparable to what can be achieved in non-saline conditions. Barley yield exceeded 5 tons per hectare and about 4.5 tons as dry biomass despite irrigation with saline groundwater, and millet produced more than 3.5 tons grain yield”.
Guidelines to produce crops on salt-affected soils
Based on the experience of experts in the different countries, Guidelines for Salinity Assessment, Mitigation and Adaptation Using Nuclear and Related Techniques have been developed to disseminate knowledge on the sustainable use of saline lands and brackish water, and on salt-tolerant trees and crops in arid lands.
“These guidelines can be used for all types of saline soils, helping farmers in various regions to scale up their production,” said Zaman.
Soil moisture neutron probe and the nitrogen-15 isotopic technique
Soil moisture neutron probes are used to monitor moisture levels in soil. During measurements, the probe is inserted into the ground and the emitted neutrons collide with hydrogen atoms of water also present in the soil. The collision slows down the neutrons – the higher the number of hydrogen atoms, the more the neutrons are slowed down – and this change in neutron speed is detected by the probe to provide a reading that corresponds to the moisture level in the soil. The more of the detected slow neutrons, the higher is the level of moisture.
Nitrogen is a key component of soil and fertilizers that plays an important role in plant growth and photosynthesis, the process through which plants convert energy from sunlight into chemical energy. As nitrogen atoms interact with the atoms in soil, fertilizer and water, they change into forms taken up by plants, released in the air, or absorbed further into the ground. Fertilizers labelled with nitrogen-15 (15N) stable isotopes — atoms with an extra neutron — enable scientists to track the isotopes to determine how effectively the crops are responding to and taking up the fertilizer. This method is called the nitrogen-15 isotopic technique, and by using this approach management practices can be improved, which in turn can help increase crop yield and optimize fertilizer use.