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Making Every Drop Count

Combating water crises through integrated soil and water management

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Each year, farmers in developing countries use some 50– 60 million tonnes of nitrogen as fertilizer. Yet, according to measurements made through the use of isotopes, less than half of that fertilizer actually reaches the crops.

When it comes to producing more crops from every drop of water by increasing water use efficiency, isotopic and nuclear techniques have an advantage over conventional techniques. They can be used as “tags” or “fingerprints” to identify how water and nutrients interact with soil components in crop and livestock production systems. They also can determine whether the water taken up by crops comes from rain, groundwater or irrigation, how it is best used by the plant and how much is actually needed for the crops to grow. This kind of information can guide farmers in making more efficient use of water and optimizing their irrigation scheduling.

Water use efficiency in agriculture. Agriculture is by far the largest global consumer of water, accounting for approximately 70 percent of freshwater withdrawn from lakes, waterways and aquifers around the world – a figure that is even higher in some developing countries and, with population growth, is projected to increase even more. This will put tremendous pressure on the agricultural sector to produce more food with less water.

Both rainfed and irrigated agriculture play important roles in meeting food demand, especially in developing countries, where some 60 percent of crop production is rainfed. Practically speaking, improving water use efficiency in agriculture requires improvements in:

  • irrigation practices – in terms of the amount, time and frequency of applications, and
  • irrigation technologies – including both drip and sprinkler irrigation.

 

Integrating soil, water and nutrient management to optimize crop production

Looking to the future, the goal of agriculture is to ensure that every drop of water is used for crop growth – whether in irrigated or rainfed production systems. Thus, it is critical to optimize soil and nutrient management by developing integrated soil-water-nutrient management practices that minimize water waste and nutrient loss. For example, it is possible to provide the necessary nutrients for plant growth with appropriate applications of fertilizer and manure and by fixing atmospheric nitrogen in the soil with legume crops. These integrated practices not only minimize water waste and nutrient loss by avoiding runoff or deep drainage beyond the crop rooting zone, they also prevent the degradation of water quality and development of soil salinity. Minimum soil disturbance and the adequate return of crop residues and animal manure can increase soil organic matter and enhance soil quality and, in turn, improve plant nutrient supply and soil water retention.

Nuclear and isotopic techniques assess, design and monitor agricultural systems

The process for identifying the proportion of water taken up by a crop from different sources such as groundwater, irrigation or rainwater involves measuring the variation in the isotopic signatures of oxygen and hydrogen. This information can be used to develop strategies for optimization and conservation of the quantity and quality of water resources in agricultural landscapes.

Rainfed agriculture: improving crop water use. Water, carbon and nitrogen are the essential components of plant life and soil organic matter. Measurements of the isotopic signatures of carbon and nitrogen in soil components can be used to assess soil, water and nutrient management practices, the results can then be applied to improve their efficient use. The carbon isotopic composition of plant materials also can be used as an indicator of salinity and drought tolerance in crops.

Irrigated cropping systems: optimizing water use efficiency. Accurate soil water measurements are needed in order to target water application. By ensuring that water is used when and where it is most essential for optimal crop growth, it is possible to minimize loss of water and nutrients. Soil moisture neutron probes measure the interaction between radiation and soil water to provide an index of soil moisture status. This makes them ideal for measuring soil water content in salt-affected soils, as salinity reduces the accuracy of conventional soil water measurement devices that use soil electrical conductivity as an index of soil moisture content.

Livestock production systems: focus on environment. Advances in water use efficiency and livestock productivity have had a positive effect on the environment. For example, there have been improvements in:

  • local feeds, in terms of their quality, availability and ration formulation,
  • livestock reproduction management and performance,
  • genetic composition of local species and breeds, leading to higher production while also conserving the genetic characteristics that enable their adaptation to harsh environments and prevailing diseases.

Livestock produced in rain-fed grazing systems and/ or fed on crop residues and agro-industrial by-products provide high quality animal protein for consumers without significantly affecting demand on water resources. Large numbers of grasses and leguminous pasture species have been evaluated and proven resistant to prolonged periods of dryness, to acid or saline soils, and to high altitude environments. They are currently being used as ruminant feed by farmers in developing countries. 

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