Objective In order to further clarify the effects of straw returning to the field under saline water irrigation on soil metabolites, the composition difference of soil specific metabolites was explored.

Methods Two irrigation water salinities, fresh water(FW) and saline water (SW), were set, and straw was applied under each water salinity, denoted by FWST and SWST, respectively. The metabolomics method of gas chromatography-time-of-flight mass spectrometry (GC-TOFMS) was used to study the metabolites in cotton soil.

Results Compared with FW treatment, SW and FWST significantly increased soil water content, total carbon, and available phosphorus contents. Compared with SW treatment, SWST significantly increased the contents of soil water content, total nitrogen, total carbon, available phosphorus, and available potassium. Compared with FW treatment, 6 and 5 metabolites of SW and FWST were significantly different, and all of them were down-regulated. A total of 28 differential metabolites were screened by SWST compared with SW treatment, with more down-regulated metabolites than up-regulated metabolites, The main types of lipids and lipid molecules were phytol, 24, 25-dihydrolanosterol, 2-monoolein, and organic oxygen compounds were trehalose. 24, 25-dihydrolanosterol was positively correlated with soil pH, and negatively correlated with soil available phosphorus, available potassium, soil water content and electrical conductivity. 2-octadecenoic glycerol and phytol were positively correlated with soil available phosphorus, available potassium, soil water content and electrical conductivity, and negatively correlated with soil pH.

Conclusion Straw returning to field can adjust the variation of soil differential metabolites by improving soil properties to cope with salt stress, which provides a theoretical basis for rational utilization of saline water resources and soil fertilization in arid areas.