Saturated hydraulic conductivity, dispersion index and water retention changes in SAS under different quality water irrigation

Abstract

Impact of different quality irrigation water viz., normal tap water (NTW, EC 0.7 dS m-1), dilute saline water (DSW, EC 5.0 dS m-1; SAR 5.0 mmol½ L-½), concentrated saline water (CSW, EC 10.0 dS m-1; SAR 5.0 mmol½ L-½), dilute alkali water (DAW, RSC 2.5 me L-1) and concentrated alkali water (CAW, RSC 10.0 me L-1) was evaluated on the physical properties of normal (pHs 7.5, ECe 1.0 dS m-1), saline (pHs 7.7, ECe 10.6 dS m-1) and alkali (pHs 9.15, ECe 2.9 dS m-1) sandy loam soils in the micro-lysimeters during growth of wheat (cv. KRL 213) and rice (cv. CSR 36). Initial saturated hydraulic conductivity (Ks) for normal, saline and alkali soil was 0.16, 0.23 and 0.005 cm h-1, respectively. Ks was reduced significantly to one fifth of initial value under CAW while DSW and CSW caused 20 and 50% increase, respectively as compared to normal soil. In alkali soil, Ks decreased significantly i.e. > 50% under DAW from its initial value of 0.005 cm h-1 and reduced to about onefifth (0.001), under CAW. While Ks increased significantly to 0.07 and 0.21 cm h-1 on the application of DSW and CSW, respectively. In post wheat samples, Ks increased by 10 to 15-times in normal soil while, 5 to 9-times in saline soil and 15 to 30-times in alkali soil under both DSW and CSW. But in comparison to post-rice soil, no effect was observed in alkali soil in post-wheat soil on alkali water application but Ks increased 5 to 10-times in normal and saline soil under saline water irrigations. Dispersion index (DI) and Ks found inversely proportional to each other in all water treatments in all three soils. Under DAW (31.3) and CAW (39.9), DI was increased significantly by 5 and 33%, respectively as compared to the initial soil. DI increased by 12 and 30% under dilute and concentrated alkali water application, respectively in saline soil. DI increased significantly with application of CAW (65.3) and decreased when irrigation was applied with DSW (37.0) and CSW (34.2), respectively. Under different quality water irrigation, soil water retention was the highest in alkali soil followed by normal and saline soils at all matric suctions. Under the application of saline water in all three soils, water retention either decreased or remains unchanged with increase in TEC of irrigation water as compared to normal tap water. Whereas under the application of alkali water, it increased in all the three soils with increase in TEC of irrigation water as compared to normal tap water application,.