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Water and soil salinity management and Sslt redistribution in irrigation systems

Vincent B., Marlet S., Vidal A., Bouarfa S., Wu J., Wang J., N'Diaye M.K., Kuper M., Zimmer D.. 2006. In : 18th World Congress of Soil Science, 9-15 juillet 2006, Philadelphie, (USA). s.l. : s.n., 1 p.. World Congress of Soil Science. 18, 2006-07-09/2006-07-15, Philadelphie (Etats-Unis).

Soil salinity is present in most of the large irrigation schemes over the world under the conjunctive effect of low quality irrigation water, aridity and lack of natural drainage ofsoils and aquifers. The trends in water management and soil salinity are assessed through studies in China, Mali, Pakistan and Uzbekistan. In China, the upper valley of the yellow river (Huinong irrigation district) is characterized by aridity, good water availability and over-irrigation. Despite large amount of drainage water returned to the river, excess in water supplied a shallow water table, accumulated in depression and resulted in soil salinity. Remote sensing showed that downstream areas are more affected by salinity and displayed lower cropping intensity. The lower valley (Bojili Irrigation District) is faced with shortage of irrigation water. Drainage water of low quality is re-used to assist leaching and get round salinity hazard.In Mali (Office du Niger), the soils are affected by an alkalinization process due to irrigation water quality. A previous reclamation of irrigation and drainage systems has modified agricultural practices and water management, and altered the trend of soil alkalinity. The improvement of surface drainage of flooded rice cropping season has decreased soil pH in clayey basins. Concomitantly the improvement of irrigation has allowed cropping during the dry season. Nowadays water stands in irrigation canal all year long and supplies a shallow water table. The recharge is high on permeable material and soil pH increases on sandy levees. In Pakistan (Chistian sub-division) shortage of irrigation surface water has lead to a significant increase in conjunctive use of groundwater of low quality. Consequently the water table and soil salinity decreased while soil sodicity increased even if leaching is improved. Whereas farmers got used to control salinity, the sodification hazard is more difficult to grasp and manage. To assess the extension of soil degradation,

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