INSIDE

TECHNICAL

COOPERATION

Vol. 3, No. 3

New Hope for Saline Soils

In many parts of the world, the soil has become so salty that normal crops cannot survive and land lies barren and unused. Without better management of irrigation, the area of land lost to agricultural production through salinity will continue to expand. But with a combination of better water management and salt-tolerant crops, the salt-affected land can be made productive again. Nuclear technology has an important role to play in achieving this objective.

Water has often been used to solve salinity problems as though there is no limit to its availability. The result on irrigated lands is often a harmful concentration of salts within the topsoil where most crops get nutrients. Soil salinity is most serious in arid and semi-arid regions where surface water is scarce and where groundwater tends to be saline. The net effect can be a white-encrusted, salt-capped wasteland. Human activities are responsible for saline conditions on about 77 million hectares globally, of which about 45 million hectares are in irrigated areas.

The challenge is making productive and sustainable use of salt-affected land, preferably by tapping the saline groundwater. What is needed is "a change in thinking," explains Dr. Mujtaba Naqvi, Manager of the IAEA's Model Project, "Sustainable Utilization of Saline Lands". "Agriculture is traditionally carried out on the basis of suiting the soil to the plant, but it is perfectly possible to suit the plant to the soil," he says. There are hundreds of species of plants that are salt-tolerant including grasses, shrubs and trees. Instead of growing salt-susceptible crops such as wheat, maize, cotton and sugarcane, tolerant plant species can be grown for use as energy sources or as timber. There are hundreds of thousands of hectares where acacia, atriplex, eucalyptus or salt-tolerant grasses are grown using saline groundwater. These are used as forage and for paper-making, and experiments are assessing the potential of using biomass from these crops for conversion. There are no ill effects to animals when they are fed on forage grown on salt-affected land.

What must be avoided is an excess of saline water and it is here that nuclear technology can be used to closely monitor moisture levels in soil and the movement of saline water. Nuclear techniques are more precise and sometimes the only means to study soil and water conditions. Neutron moisture gauges are used to measure soil water content and thus irrigation can be better managed. Nuclear techniques can also be used to analyze the composition of groundwater, and this information helps to assess the rate of recharge.

A biological approach to reclaiming salt-affected land has many advantages. The land will gradually improve in texture and fertility through the effect of the plant biomass. Soil cover by plants reduces erosion, provides shade, builds up organic matter and biological activity in the soil, transforming "dead" barren soil into a live, dynamic system.

No country can afford to waste water or abandon ever-increasing land areas to salt. Nuclear techniques can help countries to make productive and economic use of two often wasted resources, saline land and saline groundwater. Through its TC projects, the IAEA is supporting efforts toward these ends.