Abstract: With the rapid development of maize and ratoon rice production recently in the middle reaches of Yangtze River, some new double cropping systems in a whole year such as spring maizelate rice, ratoon rice have been emerged. To clarify the shortterm effects of different cropping patterns of paddy fields on soil active organic carbon fractions, carbon pool management index (CPMI) at different soil layers (0-5, 5-10, 10-20 cm) and crop yield, a field experiment was conducted at the Sanhu Farm, Hubei Province in 2017. Different cropping systems were established following a design of randomized block of early ricelate rice (DR, contrast), spring maizelate rice (MR), and ratoon rice (Rr). The results showed that, compared with DR, MR treatment reduced soil total organic carbon (TOC) concentration at different layers of paddy fields to different degrees. After harvesting the first-season crops, MR treatment significantly reduced the concentration of soil dissolved organic carbon (DOC) at all soil depths compared to DR and Rr treatments. The changes of soil microbial biomass carbon (MBC) were MR > DR > Rr. The changes of soil readily oxidizable organic carbon (ROC) concentration were DR > MR > Rr. After the second-season crop harvest, there were no significant differences in soil DOC concentrations and MBC at different layers among cropping systems. Compared to the MR treatment, soil ROC concentrations were increased by 28.22% and 47.37% at the 10-20 cm soil layer under the DR and Rr treatments, respectively, being significantly higher in Rr than in MR treatment. After the harvest of second-season crops, MR treatment increased carbon pool activity (CPA) and carbon pool activity index (CPAI) of each soil layer, whereas Rr treatment increased stable carbon and carbon pool index (CPI). From the the year-round perspective in paddy field, the soil C/N difference across different soil layers showed same tendency among different cropping systems, being Rr > DR > MR. There was no significant difference in annual total yield among different cropping patterns. From the view of sustainable agricultural development, Rr pattern is an excellent double cropping pattern of the plain area of the middle reaches of the Yangtze River.

Key words: alfalfa, organicinorganic fertilization, nitrous oxide, methane, global warming potential.