[Effects of fertilization on carbon/nitrogen ratio of maize straw and its minereffects of fertilization on carbon/nitrogen ratio of maize straw and its mineralization in soil.alization in soil].

Maize straws were collected from different treatments of two long-term fertilization studies, their carbon (C)/nitrogen (N) ratios were determined, and their C and N mineralization rates in soil were compared in an aerobic incubation test. The results showed that comparing with no fertilization, applying chemical fertilizers (NPK) or chemical fertilizers plus manure (MNPK) increased the N content and decreased the C/N ratio of maize straw. The amounts of mineralized and immobilized C and N of the straws from different fertilization treatments differed with incubation time. The straws from treatments NPK, MNPK, and N240 had significantly higher C mineralization rates than that from the treatment without fertilization. After incubation for 60 days, the straw from treatment NPK had the highest C mineralization rate (13.24% of added organic C), and the immobilized N from the straws of fertilized plots, especially of MNPK plot, was lesser, compared to unfertilized plots. Adding maize straw into soil increased the metabolic quotient (qCO2) of soil microorganisms, but the difference among the treatments was not significant. During incubation, the amounts of soil microbial biomass C and N from different treatments differed with time. Therefore, in agricultural practices, the differences in the nutrient contents of straw due to different fertilization should be considered when the straw was to be added into soil.