Effect of liming on sulfate transformation and sulfur gas emissions in degraded vegetable soil treated by reductive soil disinfestation

Reductive soil disinfestation (RSD), namely amending organic materials and mulching or flooding to create strong reductive status, has been widely applied to improve degraded soils. However, there is little information available about sulfate (SO42 −) transformation and sulfur (S) gas emissions during RSD treatment to degraded vegetable soils, in which S is generally accumulated. To investigate the effects of liming on SO42 − transformation and S gas emissions, two SO42 −-accumulated vegetable soils (denoted as S1 and S2) were treated by RSD, and RSD plus lime, denoted as RSD0 and RSD1, respectively. The results showed that RSD0 treatment reduced soil SO42 − by 51% and 61% in S1 and S2, respectively. The disappeared SO42 − was mainly transformed into the undissolved form. During RSD treatment, hydrogen sulfide (H2S), carbonyl sulfide (COS), and dimethyl sulfide (DMS) were detected, but the total S gas emission accounted for < 0.006% of total S in both soils. Compared to RSD0, lime addition stimulated the conversion of SO42 − into undissolved form, reduced soil SO42 − by 81% in S1 and 84% in S2 and reduced total S gas emissions by 32% in S1 and 57% in S2, respectively. In addition to H2S, COS and DMS, the emissions of carbon disulfide, methyl mercaptan, and dimethyl disulfide were also detected in RSD1 treatment. The results indicated that RSD was an effective method to remove SO42 −, liming stimulates the conversion of dissolved SO42 − into undissolved form, probably due to the precipitation with calcium.

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