Effect of alternating irrigation with sodic and non-sodic waters on soil properties and sunflower yield

Sunflower (Helianthus annuus L.) is moderately tolerant to soil salinity but its response to sodic irrigation is not well known. A long-term field experiment (1996–1997 to 2001–2002) was conducted on a normal sandy loam (Typic Ustochrept) soil to study the effect of alternating sodic water and good quality canal water on soil properties and sunflower yield. Irrigation treatments were: irrigation with canal water (CW), irrigation with sodic water (SW) having residual sodium carbonate of 10 mmolc L−1, one or two CW irrigation(s) alternating with one or two SW in different combinations (CW:SW, CW:2SW, 2CW:SW, SW:CW, SW:2CW, 2SW:CW). Sustained use of sodic water over 6 years increased pH and ESP of the soil and decreased final infiltration rate and achene yield of sunflower. The build-up of sodium in the soil depended upon the number of sodic irrigations given in a cyclic treatment during the season. The yield of sunflower was adequately explained (84% variation) by the build-up of Na as a consequence of using canal and sodic water in a cyclic mode. Irrespective of the rotation order, achene yield achieved in treatments involving 1CW or 2CW with 1SW (2CW:SW, CW:SW, SW:CW, SW:2CW) was about 90% (85–92%) of that obtained under CW treatment. During most of the years, the sunflower yield did not improve significantly over SW alone treatment when irrigation cycle involved two SW irrigations with one CW (CW:2SW, 2SW:CW). Alternating sodic water with canal water could, therefore, be considered in moderation as a practical way to grow sunflower in areas having sodic ground water. The sunflower can be grown reasonably well even with pre-sowing irrigation with sodic water when canal water supplies are not available at the time of sowing.