Soil organic carbon plays an important role in soil fertility and carbon sequestration. In the North China Plain, soil nutrients and organic carbon are still lacking in salt-affected soil after a successfully reclamation in the 1980 s. Our objectives were to investigate the effects of land use types under different soil management practices on soil fertility, organic carbon pools, and the microbial community at this site. Three land use types were investigated: original land without farming, farmland with residue return, and a vegetable greenhouse with farmyard manure amendment. The carbon stocks were calculated according to the equivalent soil mass method, and microbial community structure was determined by phospholipid fatty acid analysis. Over 30 years, the current concentrations of alkali-hydrolysis nitrogen, available potassium (AK), and available phosphorus increased in the three land use types, except for the AK concentration in farmland, which decreased due to the lack of potassium fertilizer input. The nutrients in the greenhouse were significantly higher than those in the original land and farmland. The carbon stocks in the original land, farmland, and greenhouse were increased by 103%, 179%, and 660%, respectively. Both land use types and seasons influenced particulate organic carbon, chemical-labile organic carbon, and microbial biomass carbon. The microbial community structures were distinctly different between the three land use types. Overall, the soil available nutrients and carbon stocks increased compared to their 1980 levels in the three land use types, and labile carbon pools and microbial community structure exhibited different responses in the three land use types. Compared to spontaneous development, mineral fertilization and organic amendment are more effective for recovering soil fertility in reclaimed soils.
