Response of Soil and Crop to Mixed Irrigation Using Brackish and Reclaimed Water

Abstract

HighlightsMixed irrigation with brackish water-reclaimed water was introduced.IBRv2 was used to evaluate the effects of mixed irrigation on the soil–crop system.Reclaimed water could be used as an alternative source of freshwater to mix with brackish water, and the suitable mixed proportion should be 1:1 based on IBRv2.Abstract. To explore the reasonable utilization of brackish water in areas where freshwater is scarce, we used pot experiments to study the physical, chemical, and biological properties of soil and crop yield characteristics under mixed irrigation using brackish–reclaimed water at different ratios. There were six treatments, including brackish water irrigation (T1); mixed irrigation using brackish–reclaimed water at 1:1 (T2), 1:2 (T3), and reclaimed water irrigation (T4); pots with plants irrigated with freshwater (CK2); and pots without plants irrigated with freshwater (CK1) as the control. The salinity of the brackish water was 3 g L-1 (6.1 dS m-1). The results indicated that compared to T1, with the increase in the proportion of reclaimed water in the mixture, the water and salt contents in the soil gradually decreased significantly; the K+, Ca2+, and SO42– contents demonstrated an increasing trend; the Na+, Cl–, HCO3–, and Mg2+ contents showed a descending to ascending trend; and the soil water drop penetration time decreased first and then increased slightly. At the same time, the soil organic matter displayed an opposite trend, and the chlorophyll content of leaves and crop biomass both changed with an “N”-style curve. Differences existed in the responses of soil enzyme activities to different mixed water mixtures. There was a slight decrease in the enzyme activity, except for sucrase under T2 and T3. The Integrated Biological Response Version 2 (IBRv2) scored 3.97 in T2. Therefore, considering the characteristics of the soil and crop and the limits of reclaimed water, reclaimed water could be used as an alternative source of freshwater to mix with brackish water, and the suitable mixed proportion should be 1:1 based on IBRv2. Keywords: Brackish water, IBRv2, Reclaimed water, Repellency.