Millet Production under Different Irrigation Strategies with Saline Water in Arid Conditions of Tunisia

A field study was conducted in Southern Tunisia to evaluate the effects of irrigation strategies with saline water (7.0 dS m-1) on soil salinity, yield and water use efficiency of Pearl millet (Pennisetum glaucum (L.) R.Br.). Millet was grown on a sandy loam soil under four irrigation treatments as low frequency irrigation for the whole season (L); high frequency irrigation for the whole season (H); low frequency irrigation until the beginning of flowering, high frequency irrigation during flowering and grain filling stages and low frequency irrigation after flowering and grain filling (LHL) and high frequency irrigation until the beginning of flowering, low frequency irrigation during flowering and grain filling stages and high frequency irrigation after flowering and grain filling (HLH). The actual irrigation frequencies for the treatments L and H were dictated by the degree of soil water depletion within the root zone before the next irrigation. Irrigations were applied when 70 and 40% of the total available water in root zone had been depleted, respectively, for L and H treatments. Yield, yield components, water supply and soil salinity were measured. The results showed that soil salinity values remained lower than that of ECiw and were significantly affected by irrigation treatments. Higher soil salinity was maintained in the root zone with H and HLH than L and LHL irrigation treatments. Millet yields were maximized under the L treatment and yields in this treatment averaged 22 and 12.4% more grain and dry matter than the H treatment, respectively. No significant differences were observed in grain yield, dry matter production, panicle no m-2, kernel number/panicle and 1000-kernel weight from the comparison between L and LHL treatments. With L and LHL treatments, 17.9 and 13.5% of the irrigation water was saved in comparison with H irrigation treatment and WUEg increased by 35 and 26% compared with that of H irrigation treatment. L and LHL irrigation treatments provide significant advantage for both yield and WUE and reduce the build-up of salinity compared to the H and HLH irrigation practices in millet production under experimental conditions. For water-saving purposes, the L and LHL irrigation strategies were found to be a useful practice for scheduling millet irrigation with saline under the arid Mediterranean conditions of Southern Tunisia.