Approximately 70 per cent of global freshwater consumption is used in the agricultural sector, yet water use efficiency in many countries is below 50 per cent. Nuclear and isotopic techniques provide data on water use including losses through soil evaporation and help optimize irrigation scheduling and improve water use efficiency.
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Agricultural water management
The FAO forecasts that by 2050 global water requirements for agriculture will increase by 50 per cent to meet the increased food demands of a growing population. Global freshwater is becoming increasingly scarce, due to improper management, indiscriminate use and a changing climate. Water scarcity and quality problems in many parts of the world are a serious challenge to future food security and environmental sustainability.
Addressing these issues requires an improved management of land and water. Jointly with the FAO, the IAEA helps Member States develop and adopt nuclear-based technologies to optimize agricultural water management practices that support the intensification of crop production and the preservation of natural resources.
Using science to better conserve water resources
To ensure food security and sustainable water management for agriculture, there is an urgent need to produce more crop per drop of water used in the agricultural sector and hence ensure that water use efficiency is increased without negative impacts on downstream water quantity and quality.
Improvements in the handling of water resources must be built on an integrated approach to soil-water-plant-nutrient management. This should include optimizing irrigation scheduling and more efficient irrigation systems, such as drip irrigation. Soil fertility needs to be improved to ensure that crop growth is not limited by nutrient or physical constraints and every drop of water can be fully utilized for growth. Efficient water uptake by crops can be achieved through demand-based irrigation scheduling that takes account of different crop’s water needs, growth stages and the prevailing environmental conditions.
Agricultural water use efficiency can be improved by minimizing soil evaporation losses relative to plant transpiration in the field. The ability to quantify soil evaporation and plant transpiration provides information on irrigation amount for specific crop types and growth stages, which play key roles in the conservation and management of water.
How nuclear and isotopic techniques contribute
Nuclear and isotopic techniques play an important role in providing information essential to developing strategies for the improvement of agricultural water management:
- Isotopic signatures of oxygen-18 and hydrogen-2 in the water taken from field crops allow the separation of irrigation water into soil evaporation and crop transpiration, thereby providing information essential for improving the water use efficiency of crops.
- The soil moisture neutron probe is ideal for measuring soil water in the immediate vicinity of crop roots, providing accurate data on water availability. This helps establish optimal irrigation schedules and is the most suitable instrument for measuring soil moisture under saline conditions. It is also widely used to calibrate conventional moisture sensors.
- The isotopic signature of nitrogen-15 is used to trace the movement of labelled nitrogen fertilizers in soil, crops and water, essential to identifying factors that potentially affect nitrogen fertilizer use efficiency and water quality in agricultural landscapes. The combined isotopic signatures of nitrogen-15 and oxygen-18 in nitrate enable the identification and segregation of sources of nitrate pollution in agricultural catchments.
- The cosmic ray neutron probe is used to assess water fluxes at landscape level to establish sustainable land and water use management strategies.
