The use of saline water of the Caspian sea for irrigation and barley production in northern Iran

Abstract

A rapid increase in the population of Iran during the past two decades has significantly increased the countries need for food and fibre and has put its land and water resources under sever stress. Freshwater resources of the country, both surface and ground water, has been over-exploited, often at the expense of deteriorating both water and land quality. With a limited room for expanding irrigation agriculture due to the lack of extra capacity in the country's freshwater resources, the possible use of Caspian Sea water, whose salinity is well below that of the open seas and oceans, has a some appeal. With its potential hazard of increasing land and ground-water salinity as well as possible deterioration of soil physical, chemical and biological characteristics, the issue needs to be thoroughly researched. The main objective of this project is to study the impact on crop yield and soil characteristics of using the Caspian Sea water, mixed with well water, for irrigation. Experiments were carried out during 2001-2002 growing season with three irrigation regimes of well water (with a salinity level of 0.8 dS/m); Caspian seawater (EC = 21.5 dS/m) diluted with the well water at a 1:1 ratio and used either at the time of stem formation or prior to flowering stage. The soil was a silty loam with EC = 16.2 dS/m. The results of both pot and field experiments show that a 1:1 mixture of Caspian See water and well water can be used for irrigation without a significant reduction in barley production. This would amount to a significantly reduced in demands on the limited groundwater resources of the region for agricultural use. The results of soil analysis before planting and after harvest show that EC had increased, more specially with the irrigation regime which starts earlier in the season (at the time of stem formation). This may suggests that the mixing of sea and ground waters at the rates used in these experiments may not be sustainable over time and there may be a risk of soil salinization. Further experiments with different mixing rates of Caspian Sea water and bore water and the calculation of LR to stablize soil salinity are in progress. The option of establishing a drainage system to remove excess salts from the profile either by rain or by adding the calculated LR to volume of irrigation water is under investigation.