Distribution of soil water, salt and water drop penetration time (WDPT) under two-point-source trickle irrigation with sewage water

Laboratory two-point-source overlap sewage trickle irrigation experiments were conducted to assess the effects of sewage irrigation rates on soil water repellency, water movement and salt transport. Four flow rates, i.e. 1.08, 2.17, 5.0 and 10.0 mL·min-1 were calibrated and applied to three typical soil types. The characteristics, including soil water repellency, wetting patterns and soil salt content distributions were analysed. The results showed that: (1) After short-term (shorter than half a day) sewage irrigation and redistribution, water drop penetration time (WDPT) increased evidently. WDPT increments were the smallest for sand, but the most significant for saline-alkali soil. The larger the flow rates, the longer the WDPTs. (2) The wetting fronts for sand and Lou soils were both smooth, but irregular for saline-alkali soil. Discharge rates of 5 to 10 mL·min-1 was suitable irrigation rates for sand and Lou soils. Low application rate (i.e., 1.08 mL·min-1 or smaller) was recommended for saline-alkali soil. Power functions were good for quantifying the relationship of horizontal and vertical wetting fronts with respect to time. (3) The distributions of soil salt content and WDPT in horizontal and vertical planes were highly consistent with those of soil water content. Saline-alkali soil with low salt content was found more hydrophobic. In conclusion, short-term sewage trickle irrigation affected distribution of soil water, soil salt and WDPT. © 2018 Technoscience Publications. All rights reserved.