Characterization of drain discharge from subsurface drainage system with 40 m lateral spacing in saline vertisols of Tungabhadra command area

Abstract

Characterization of drain water for irrigation over the cropping (rice) season was assessed during rabi 2020-21 at Agricultural Research Station, Gangavati in the Tungabhadra Command Area (TBP). Drain water samples collected fifteen times over the cropping season from man holes revealed that the pH and EC values of drain water varied from 7.33 to 7.00 with a mean of 7.16 and 6.64 to 5.94 dS m-1 with a mean of 6.22 dS m-1 respectively. The SAR and RSC values in drain discharge varied from 21.80 to 14.60 (mmol/L)1/2 with a mean value of 17.20 (mmol/L)1/2 and from 13.20 to 0.00 me L-1 with a mean value of 2.69 me L-1. The DCR and SSP in drain discharge varied from 0.28 to 0.17 with a mean value of 0.23 and from 83.3 to 71.8 with a mean value of 76.5 respectively. The Mg/Ca and Cl/SO4 ratios in drain discharge varied from 12.70 to 0.29 with a mean value of 1.92 and from 0.63 to 0.31 with a mean value of 0.49 respectively. Due to higher values of EC, SAR, RSC and SSP then the recommended quality standards of irrigation water quality, at present the drain water was found not suitable to be used directly for irrigation purposes.