Improved Decision Making for Deficit Irrigation of Wheat in Northern Syria

Abstract

Increasing water scarcity due to population growth and urbanization is pushing the countries in the Mediterranean region to improve their irrigation water use efficiency. Supplemental irrigation of rain-fed crops is a very efficient use of the scarce water resources, but farmers often apply more water than is actually needed. The objectives of this study were to evaluate a model for scheduling of supplemental irrigation based on daily climate data and to assess irrigation requirements under different irrigation management options in northern Syria. The model used the FAO daily reference evapotranpiration and dual crop coefficient procedure for estimating irrigation requirements, but an addition was made to allow the storage of soil moisture below the developing root zone of rain-fed crops. The model performed satisfactorily for three years of data from a wheat trial at Tel Hadya in northern Syria, which has an average annual rainfall of 356 mm. The tested irrigation management options included the application of full irrigation at 50% depletion of the available soil water and irrigation of 67% of the soil water depletion at 75% of the available soil water (deficit irrigation). The deficit option was especially efficient in wet years, saving up to 84 mm, compared to full irrigation. The model will be further evaluated and developed in to an irrigation decision support tool.