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Field experiments were conducted on a saline vertisols during 2000�2002 for evaluating the response of cotton (Gossypium hirsutum L.) to applied irrigation water (IW, 0.8, 1.0, 1.2 and 1.4 times the evapotranspiration, ET) with drip and furrow irrigation method in four different blocks varying in soil salinity (ECe, surface 0.6 m) and water table depths (WT). The initial ECe and average WT for the blocks I, II, II and IV were 8.0 ± 0.4, 1.25 ± 0.08; 9.1 ± 0.7, 1.15 ± 0.08; 10.4 ± 0.5, 1.05 ± 0.09 and 15.1 ± 0.8 dS m-1, 0.95 ± 0.07 m, respectively. The growth and yield performance of cotton irrigated through furrows, even though with good quality canal water (ECw 0.25 dS m-1), was poor when compared with drip irrigation with marginally saline water (ECw 2.2 dS m-1). The crop responded to applied water and the maximum cotton yield (1.78 Mg ha-1�average for two years) was obtained from block I under drip irrigation applied at 1.2 ET while the lowest yield (0.18 Mg ha-1) was from block IV when applied water equaled 0.8 ET with furrow irrigation. Due to creation of better salt and moisture regimes, water productivity also considerably improved with drip irrigation. Production functions developed could be represented as: Y (Mg ha-1) = 0.2070 AW - 0.0012 AW2 + 0.0807 ECe - 0.0049 ECe2 - 0.0014 AW × ECe - 6.5945 (R2 = 0.974**) for drip irrigation and Y = 0.3853 AW - 0.0021 AW2 + 0.0253 ECe - 0.0005 ECe2 - 0.0016 AW × ECe - 14.9117 (R2 = 0.877**) for furrow irrigation where AW and ECe represent applied water and time weighted mean soil salinity, respectively. Though the gross income (US$ 223�690 ha-1) was more with drip than furrow (US$ 67�545 ha-1) irrigation, the net profit per unit of applied water was higher with furrow irrigation. It was concluded that the drip system provide for opportunities to enhance the use of saline waters in water scarcity areas especially those existing at the tail end of canal commands. |
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