Abstract
The use of unconventional water resources is an effective way to alleviate the scarcity of freshwater resources, especially in areas where freshwater is scarce, but reclaimed water is abundant. To explore the reasonable utilization of brackish water and reclaimed water, a pot experiment was carried out to study the risk of secondary soil salinization. The experiment set two salinity levels of brackish water, four mixed irrigation ratios of brackish water and reclaimed water, and freshwater irrigation as the control. The results showed that: (1) Soil moisture content, salt content, pH, ESP, and SAR decreased with the increase in the proportion of reclaimed water in the mixture. (2) Soil exchangeable Ca2+ content under mixed irrigation was higher than that of brackish water irrigation and reclaimed water irrigation. The content was especially significantly higher under the 1:2 mixed irrigation with brackish-reclaimed water. With the increase of the proportion of reclaimed water in the mixture, soil exchangeable Na+ content decreased, and a significant difference was found between treatments. The soil exchangeable K+ decreased at first and then increased, while the soil exchangeable Ca2+ increased at first and then decreased. The trend of the change of soil exchangeable Mg2+ content was similar to that of soil exchangeable Ca2+ content. (3) Based on the soil pH value, there was no risk of soil alkalization in all treatments. Based on ESP, ESP was less than 15% under freshwater irrigation, brackish (3 g/L)-reclaimed water 1:2 mixed irrigation, and reclaimed water irrigation, indicating no risk of alkalization. However, other treatments may cause soil alkalization. (4) At 3 g/L of brackish water, there was a salinization risk when the proportion of reclaimed water in the mixture was less than 1/2, but there was no salinization risk when the proportion was greater than 1/2. At 5 g/L of brackish water, there was a salinization risk under mixed irrigation. Therefore, the mixed irrigation of brackish water and reclaimed water had the risk of secondary soil salinization, and the appropriate salinity and mixing ratio should be selected.
Highlights
The shortage of global water resources, environmental pollution, and intensified salinization of soil are some of the issues facing agricultural production and environmental management at the start of this century [1]
Based on exchangeable sodium percentage (ESP), ESP was less than 15% under freshwater irrigation, brackish (3 g/L)-reclaimed water 1:2 mixed irrigation, and reclaimed water irrigation, indicating no risk of alkalization
ESP was less than 15% in freshwater irrigation and reclaimed water irrigation, and there was no risk of alkalization
Summary
The shortage of global water resources, environmental pollution, and intensified salinization of soil are some of the issues facing agricultural production and environmental management at the start of this century [1]. A variety of environmental factors, such as strong winds, extreme temperatures, soil salinity, droughts, and floods, affect the production and cultivation of agricultural crops, of which soil salinity is one of the most destructive environmental pressures, resulting in a significant decline in the area of arable land and crop productivity and quality [1,2]. The salt content of irrigation water in brackish water irrigation areas is the main factor restricting crop yield, and mixed irrigation or rotation irrigation using reclaimed water and brackish water can alleviate the pressure of the shortage of agricultural water resources, as well as increase crop yield and improve soil salt accumulation in brackish water irrigation areas. It is of great significance to study the effect of mixed irrigation using brackish water and reclaimed water and its effect on secondary soil salinization
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