Effect of irrigation with saline water on soil and crop in South-West Spain

The drained and irrigated marshes of the Guadalquivir river (SW Spain) are formed on soils of high clay content (about 70%), high salinity, and a shallow, extremely saline, water table. Irrigation is necessary for successful crop production in this region of low and variable rainfall. In some years, however, water supply for irrigation is limited due to drought periods, and farmers are obliged to irrigate with river water, which at this location is of high salinity due to tidal flow. The objective of this work was to evaluate the effects of irrigation with water of high salinity on soil properties and growth and yield of cotton crop. The experiments were carried out during 1997. Irrigation was applied by furrows. Water content profile, tensiometric profile, water table level, drainage water flow, soil salinity, leaf water potential, stomatal conductance, and crop development and crop yield were monitored. The results showed that after the irrigation with saline water, the soil salinity increased. This increase was more noticeable in the top layer (0-30 cm depth). After five irrigations with water of good quality, the salinity of the soil in the subplot irrigated with saline water leached values similar to those before the application of saline water. The irrigation with saline water affected crop development. Despite the negative effects on crop development and water status in plants, the crop yield was the same as on the subplot irrigated with nonsaline water.