Irrigation with saline water in the reclaimed marsh soils of south-west Spain: impact on soil properties and cotton and sugar beet crops F. Moreno a,* , F. Cabrera a , E. Ferna Ândez-Boy b , I.F. Giro Ân a , J.E. Ferna Ândez a , B. Bellido c a Instituto de Recursos Naturales y Agrobiologõ Âa de Sevilla IRNAS-CSIC), P.O.Box 1052, 41080 Seville, Spain b Departamento de Cristalografõ Âa, Mineralogõ Âa y Quõ Âmica Agrõ Âcola, University of Seville, P.O.Box 553, 41080 Seville, Spain c Comunidad de Regantes, Sector B-XII Bajo Guadalquivir), Lebrija, Spain Accepted 4 July 2000 Abstract The drained and irrigated marshes in south-west Spain are formed on soils of alluvial origin from the ancient Guadalquivir river estuary. The most important characteristics of these soils are the high clay content about 70%), high salinity, and a shallow, extremely saline, water table. The reclaimed area near Lebrija, called Sector B-XII about 15,000 ha), has been under cultivation since 1978. Some years, however, water supply for irrigation is limited due to drought periods. The objective of this work was to evaluate the effects of irrigation with high and moderately saline waters on soil properties and growth and yield of cotton and sugar beet crops. The experiments were carried out during 1997 and 1998 in a farm plot of 12.5 ha 250 m  500 m) in which a drainage system had been installed, consisting of cylindrical ceramic sections 0.3 m long) forming pipes 250 m long, buried at a depth of 1 m and spaced at intervals of 10 m. These drains discharge into a collecting channel perpendicular to the drains. Two subplots of 0.5 ha 20 m  250 m) each were selected. In 1997 cotton was growing in both subplots, and irrigation was applied by furrows. One subplot A) was irrigated with fresh water 0.9 dS m 1 ) during the whole season, while in the other subplot B) one of the irrigations at ¯owering stage) was with water of high salinity 22.7 dS m 1 ). During 1998 both subplots were cropped with sugar beet. Subplot A was irrigated with fresh water 1.7 dS m 1 ) during the whole season, while in subplot B two of the irrigations were with moderately saline water 5.9±7.0 dS m 1 ). Several measurement sites were established in each subplot. Water content pro®le, tensiometric pro®le, water table level, drainage water ¯ow, soil salinity, and crop development and yield were monitored. The results showed that after the irrigation with high saline water subplot B) in 1997 cotton), the soil salinity increased. This Agricultural Water Management 48 2001) 133±150 * Corresponding author. Tel.: 34-95-4624711; fax: 34-95-4624002. E-mail address: fmoreno@irnase.csic.es F. Moreno). 0378-3774/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII:S0378-377400)00120-7