A review on secondary soil salinization caused by reclaimed water irrigation

Water scarcity is a major challenge facing agricultural production in China. Unconventional water resources such as reclaimed wastewater can be used as a complimentary resource for irrigation. However, reclaimed wastewater is rich in salt and its long-term use for irrigation could lead to secondary soil salinization. In this review, we analyze the factors that have potential effects on accumulation of salt in soil. They include irrigation method, soil texture, crop types and crop variety, irrigation time, and reclaimed wastewater modification. Results show that our current understanding of the effect of long-term reclaimed water irrigation on soil salt accumulation is still unclear. As a result, more systematic studies are needed to elucidate the main factors that affect salt accumulation in soil. While reclaimed water modification is promising, more studies are required before it can be widely implemented. We suggest that future research on reclaimed water irrigation should focus on field experiments to systematically study how irrigation method, soil texture, crops, agronomic management and reclaimed water modification interactively affect salt accumulation in soils irrigated with reclaimed wastewater.