Characterization of drain discharge from subsurface drainage system with 60 m lateral spacing in saline Vertisols of Tungabhadra command area

Abstract

Characterization of drain water for irrigation over the cropping season was assessed during rabi/summer 2020-21 at Agricultural Research Station, Gangavati in the TBP command area. 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 7.55 to 7.09 with a mean of 7.27 and 5.25 to 4.33 dS m-1 with a mean of 4.73 dS m-1 respectively. The SAR and RSC values in drain discharge varied from 25.20 to 18.10 (mmol/L)1/2 with a mean value of 21.60 (mmol/L)1/2 and from 11.50 to 9.50 me L-1 with a mean value of 9.00 me L-1. The DCR and SSP in drain discharge varied from 0.19 to 0.12 with a mean value of 0.14 and from 88.40 to 80.90 with a mean value of 85.60 respectively. The Mg/Ca and Cl/SO4 ratios in drain discharge varied from5.00 to 0.13 with a mean value of 0.98 and from 1.80 to 0.97 with a mean value of 0.63 respectively. The EC, SAR, RSC, and SSP values of drain water are the major constraints as far as their irrigation feasibility is concerned.