Optimum Groundwater Table Depth and Irrigation Schedules for Controlling Soil Salinity in Central Iraq

Abstract

Excessive irrigation and poor drainage conditions are the major factors contributing to rising groundwater tables and soil salinity in the irrigated areas of Central Iraq. Therefore calculations of precise irrigation requirements are necessary to optimize crop production and keep the groundwater table below the root zone to avoid soil salinization. In this study, the soil–water–atmosphere–plant (SWAP) model is used to determine optimal groundwater table depth and irrigation amounts for the study area. SWAP was calibrated using field data from the study area during the wheat and maize season of 2011–2012. The modelling results reveal that under current irrigation practices (600 mm to wheat and 1000 mm to maize), more than 30% water is lost as deep percolation. This causes a rise in the groundwater table and reduction in crop yields. The model simulations suggest that a groundwater table depth of 200 cm together with an irrigation application of 500 mm to wheat and 600 mm to maize will be the best combination to attain optimal yields. Therefore a drainage system in these areas should be installed to maintain groundwater table depth around 200 cm. Maintaining adeeper groundwater table will not be suitable as costs will increase and crop responses negligible. For long‐term sustainability, rehabilitation of existing drainage systems to evacuate excessive salts from the root zone will be imperative. Copyright © 2013 John Wiley & Sons, Ltd.

Modeling the effects of different irrigation schedules and drain depths for soil salinity management: A case study from Southern Iraq

“…To ensure long-term sustainability of irrigated agriculture in these areas, rehabilitation of existing drainage systems should be done on priority basis. These results are consistent with the findings of Qureshi et al (2013).…”

“…SWAP is designed to simulate unsaturated flow and solute transport and has successfully been applied in the field of agriculture and water management under variety of climatic and environmental conditions (Qureshi et al 2010(Qureshi et al , 2013. SWAP is designed to simulate unsaturated flow, solute transport, heat flow and crop growth in the soil-plant-atmosphere environment at the field scale.…”

“…Data on rooting depth, leaf area index (LAI) and soil cover values as a function of crop development stage were taken from Qureshi et al (2013). The threshold values for salinity stress for wheat and maize were taken as 6.0 and 1.7 dS m -1 , respectively (Mass and Hoffman, 1977).…”

“…The h1 to h4 values refer to the sink term theory of Feddes et al (1978). The sink term values for this study were taken from Qureshi et al (2013). The agronomic and crop parameters used in this study are summarized in Table 1.…”

Geospatial Assessment of Irrigation Water Potential for Black Soil Salinization

“…GIS modelling methods were used for monitoring salinization and isolating areas by indicators and weight (Eklund, Kirkby and Salim 1998).Timely installation of drainage infrastructure can help in eliminating the onset of drainage associated soil salinity problems in the irrigated areas (Qureshi et al, 2013).…”