Soil Salinity in the Central Arid Region of Iran: Esfahan Province

Abstract

Soil salinity in the central arid region of Iran is mainly due to dry climate, salt-rich parent materials, insufficient or lack of drainage and use of saline groundwater for irrigation. Esfahan province is located in the central arid region of Iran. Of 105,000 km² total area, an area of 5,000 km² is used for crop and fruit production. Soil and water salinity is the major limitation to achieve optimum crop yields. The soils are classified as Entisols and Aridisols. Soil salinity is distributed in nine physiographic land forms, namely, mountains, hills, plateau, piedmont plain, alluvial plain, lowland, flood plain, colluvial fan and alluvial fan. In this study, salinity data were obtained from soil survey project reports conducted in the last decade. The data showed the ECe varied to a large extent. The highest and lowest average salinities were 38.3 dS m⁻¹ in the lowland (high evaporation and ground water table) and 0.6 dS m⁻¹ in the mountainous area, respectively. High precipitation over evaporation in the mountainous area of west leached salts from soil profile. The ECe values are moderately high to extremely high in the east part of Zayandeh-Rud river plain due to fine soil texture and poor drainage. In the river plain, irrigation often causes secondary soil salinization. More work is required to establish real causes of soil salinization and spatial distribution in the province. However, it is evident that salinity distribution is highly variable in the central arid region of Iran and in different physiographic unit of land area. Future development of agriculture and industry in each landform should consider the present and future soil salinity potential. Given the importance of irrigated agriculture and the shortage of water supply, more ground-based soil and groundwater salinity monitoring schemes are needed as a prerequisite of land use in the region.