Short-term carbon mineralization in saline-sodic soils

Previous studies have shown that carbon (C) mineralization in saline or sodic soils is affected by various factors including organic C content, salt concentration and water content in saline soils and soil structure in sodic soils, but there is little information about which soil properties control carbon dioxide (CO2) emission from saline-sodic soils. In this study, eight field-collected saline-sodic soils, varying in electrical conductivity (ECe, a measure of salinity, ranging from 3 to 262 dS m(-1)) and sodium adsorption ratio (SAR(e), a measure of sodicity, ranging from 11 to 62), were left unamended or amended with mature wheat or vetch residues (2% w/w). Carbon dioxide release was measured over 42 days at constant temperature and soil water content. Cumulative respiration expressed per gram SOC increased in the following order: unamended soil < soil amended with wheat residues (C/N ratio 122)< soil with vetch residue (C/N ratio 18). Cumulative respiration was significantly (p < 0.05) negatively correlated with ECe but not with SAR(e). Our results show that the response to ECe and SAR(e) of the microbial community activated by addition of organic C does not differ from that of the less active microbial community in unamended soils and that salinity is the main influential factor for C mineralization in saline-sodic soils.