Features: Saline Soils

Salt of the Earth

The problem of salt in agriculture is not new, or limited to the countries participating in the IAEA's project. Worldwide, FAO experts estimate that salinity affects productivity on about 80 million hectares of arable land - just about the total land area of a country the size of Pakistan - predominately in developing countries having hot and dry climates.

The problem arises when salt is left behind in the soil as water passes back into the atmosphere through the processes of evaporation and plant transpiration. In areas with good rainfall and effective drainage systems, the soluble salts change in composition and concentration as water carries them away, eventually to the seas. But in parts of the world having little rainfall and restricted drainage, the salts cannot easily be transported, and accumulate in lowlands, or in the groundwater below them.

Nature's own geographical and geological processes are a major contributor to salinity. Experts say that more than 30 million hectares of salt-affected land arise from natural causes, aridity, and high rates of evaporation. In many cases, problems are exacerbated by the loss or destruction of natural vegetation from animal grazing or the search for biomass to burn for cooking and heat.

Most saline lands, however, are in or near areas where irrigation is the backbone of farming, predominately developing countries. Lack of good drainage is a major contributor to salinity. So is seepage from irrigation systems and drainage fields which can lead to a loss of nearly half of the water. Gradually the groundwater table rises, bringing salts to soil layers where crops get nutrients. The result is stunted or dead plants. As surface waters evaporate, the fields become white encrusted, salt-capped wastelands. Farmers abandon them and agricultural economies suffer.

Salinity can be controlled, and lands reclaimed, though not overnight and not easily or inexpensively. One approach is constructing good irrigation systems that gradually improve soil conditions and prevent formation of waterlogged and unproductive fields. Systems need to apply slightly more water than the crop needs, to promote leaching, and then drain and catch groundwater so that it can be recyled for agricultural or industrial uses.

Unfortunately, poor irrigation practices often promote rather than control salinity, and engineered drainage systems extending over large areas of land are financially out of reach for most countries. The World Bank, for example, has estimated that about $600 billion needs to be invested globally in rural and urban water delivery systems.

Biosaline agriculture - suiting salt-tolerant plants to soil and water conditions - may offer a more affordable alternative, though not necessarily an easier one. It depends upon good irrigation practices, especially where the groundwater already has higher than normal salt concentrations. And it takes years of research and testing to match the right plants with the right soil and water conditions, then maintain the ecological balance for sustainable agricultural production.

Whatever the selected approach, experts agree on the need for greater investment in collaborative campaigns to control salinity. Each year, hundreds of millions of dollars -- no one knows exactly how much -- are lost to national agricultural economies from saline lands and desertification processes.

More certain is that in years ahead, the world's population growth, especially in developing countries, will heighten needs for productive land, food and water, about 70% of which is used for agriculture. Irrigated farmlands today supply about half of the world's food and fiber, and far more in countries where farmers rely upon groundwater for their harvests.

The drive for sustainable development charts a challenging course for international cooperation. The world's blueprint for action -- Agenda 21, which governments adopted in 1992 at the Earth Summit and comes up for decennial review in June 2002 -- set ambitious targets. It called for a multi-year range of integrated activities exceeding $31 billion to promote sustainable agricultural and rural development, including concerted action against salinity, land degradation, and desertification. Strong emphasis was placed on closing gaps of "insufficient basic knowledge" and in wider applications of science and biotechnology.

Plant

As it seeks to expand its reach, the IAEA project is contributing to progress. Farmers and scientists are working together to factually feed the knowledge base upon which bigger development programmes must be built. If more farming communities can be enlisted in the fight to reclaim wastelands, their work could stimulate broader-based partnerships for progressive agriculture in needy countries.

With more hands joined for the productive transfer of knowledge and technologies, life on the farm can change. Until then, farmers on saltlands like those in Sed El Masjoune face little choice but to plough ahead in the best way they know how.

Written and photographed by Lothar Wedekind, IAEA Division of Public Information. IAEA.org presentation by Rodolfo Quevenco, with technical, editorial and image support from Horace Agbogbe, Lydia Baben and Dean Calma.

For more information on this IAEA project, contact Mr. Jorge Morales, Department of Technical Cooperation.