Abstract
A two-year study was conducted in arid region of Tunisia to evaluate the effects of deficit irrigation regimes with saline water on soil salinity, yield, and water use efficiency of onion grown in a commercial farm on a sandy soil and drip-irrigated with water having an of 3.6 dS/m. Irrigation treatments consisted in water replacements of accumulated at levels of 100% (SWB-100, full irrigation), 80% (DI-80), 60% (DI-60), when the readily available water in the control treatment (SWB-100) is depleted, deficit irrigation during ripening stage (SWB100-MDI60) and farmer method corresponding to irrigation practices implemented by the local farmers. Results on onion production and soil salinization are globally coherent between the two-year experiments and show significant difference between irrigation regimes. Higher soil salinity was maintained in the root zone with DI-60 and farmer treatments than full irrigation (SWB-100). SWB100-MDI60 and DI-80 treatments resulted also in low values. No significant differences were observed in bulbs fresh and dry yields, bulbs number·ha−1and weight from the comparison between full irrigation (SWB-100) and deficit treatments (DI-80, SWB100-MDI60). DI-60 irrigation treatment caused significant reductions in the four parameters considered in comparison with SWB-100. The farmer method caused significant reductions in yield components and resulted in increase of water usage 45 and 33% in 2008 and 2009, respectively. Water use efficiency was found to vary significantly among treatments, where the highest and the lowest values were observed for DI-60 and farmer treatments, respectively. The full irrigation (SWB-100) and deficit irrigation (DI-80 and SWB100-MDI60) strategies were found to be a useful practice for scheduling onion irrigation with saline water under the arid Mediterranean conditions of southern Tunisia.
Highlights
Water scarcity is an increasingly important issue in many parts of the world
Efficient use of saline water by irrigation is becoming increasingly important, and alternative water application method such as drip may contribute substantially to attain the twin objectives of higher productivity and optimum use of water
The field experiment was carried out during the growing season of 2008 and 2009, between the months of March and August, in the southern east of Tunisia in a commercial farm situated in Medenine
Summary
Climate change predictions of increase in temperature and decrease in rainfall mean water will become even scarcer. This is especially the case in arid regions of Tunisia subject to frequent droughts and where restricted supply of good quality water is the most important factor limiting crop production. Efficient use of saline water by irrigation is becoming increasingly important, and alternative water application method such as drip may contribute substantially to attain the twin objectives of higher productivity and optimum use of water. Currently used in arid regions of Tunisia for high-value vegetable crop production such as onions, potatoes, peppers, and lettuces, can result in considerable saving in irrigation water, reducing the risks of salinization if the correct management procedures are applied
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