[Enhanced Remediation of Cd Contaminated Soil by Cotton with DOM]

To reveal the effects of dissolved organic matter (DOM) on the remediation of cadmium (Cd)-contaminated soils by cotton, the effects of cotton straw dissolved organic matter (CM) and farmyard manure dissolved organic matter (FM) on soil available Cd (DTPA-Cd) content, cotton biomass, photosynthetic characteristics, and Cd accumulation were investigated in a pot-based experiment under three exogenous soil Cd levels (mg·kg^-1) of 0 (C0), 5 (C5), and 10 (C10). The results showed that the application of CM and FM increased the content of available Cd in soil, with the maximum increase of 30.89% and 8.51%, respectively, and that of CM was higher than that of FM. The effects of CM and FM application on total biomass and photosynthetic characteristics in cotton showed that biomass accumulation and net photosynthetic rate were promoted at the C0 level, there was no significant difference compared to that in the control (CK) at the C5 level, and total biomass accumulation and net photosynthetic rate were inhibited at the C10 level; however, transpiration rate both showed higher than the CK treatment at the same Cd level. The application of DOM altered the Cd content of all parts of the cotton compared to that in the CK treatment, where the application of CM resulted in significantly higher Cd content in all parts of the cotton (except for lint) than that in the CK treatment at the same Cd level; however, the application of FM mainly increased the Cd content in the root. The root was the main organ for the increase in total Cd accumulation, the application of CM and FM significantly increased the total Cd accumulation in cotton, and the total Cd accumulation increased by 27.76%-113.05% and 17.77%-93.79%, respectively. Therefore, DOM can be used as an additive to repair Cd-contaminated soil, which has certain application potential. It is recommended to apply cotton straw DOM to repair Cd-contaminated soil.