Impact of Using Saline Water Irrigation Strategies on Soil Salinity

Mohammad Feizi

Scientific Member of Isfahan Agricultural and Natural Resources Research Center
Soil and Water Research Division, Isfahan, Iran
e-mail: Feizim2000@yahoo.com
 

Abstract

Use of saline water for irrigation is increasing, because of the decrease in fresh water resources, increase of population, growth of industries and expansion of agriculture. One of the main concerns in the use of saline water in arid and semi-arid regions of Iran is to maintain optimum salt balance in the soil profile. In the Isfahan province, central Iran, most of the irrigation water is shallow and/or deep saline water. In some areas the farmers have access to limited amount of fresh water from river. In order to use these water resources properly, a series of studies were conducted on using saline water to produce cotton, wheat, barley and sunflower. This paper presents the effect of saline irrigation water management on soil salinity.

Seven irrigation water treatments were used: application of water with an electric conductivity (ECiw) of 2.6, 6.2 and 10 dS/m (M1, M2 and M3, respectively) throughout the season, application of water with 2.6 dS/m ECiw in early season (germination and establishment stage) and saline water of the ECiw  values of 6.2 dS/m (M4) or 10 dS/m (M5) in the rest of growth period, and alternate application of water of 2.6 dS/m ECiw with 6.2 dS/m (M6) or 10.0 dS/m (M7) ECiw values. Monitoring the effect of the treatments on soil salinity (ECe) and sodium absorption ratio (SAR) over a four year period showed that, in general, the ECe and SAR values were lower at germination and harvesting stages in comparison to the initial ECe and the salinity of irrigation water (ECiw). In the treatments where the ECe values at the beginning of the season were higher, the rate of ECe reduction was more conspicuous in comparison to the treatments with lower ECe. However, the ECe at harvest was closely correlated with the weighted average ECiw.

The study of the salt balance in the soil during four years showed that treatments M1, M6 and M4 could maintain the best salt balance in the soil. These treatments thus resulted in the highest crop yields. Alternate irrigation with ECiw of 2.6 and 6.2 dS/m (M6) resulted in almost the same yield as using irrigation water with an ECiw of 2.6 dS/m throughout the season. This could also save about 50% of fresh water (2.6 dS/m) for producing sensitive crops.