Xuecheng Liu, Huili Zhang
（Hainan University）
Abstract：
By analyzing the soil microbial biomass carbon (SMBC), microbial biomass nitrogen (SMBN), microbial biomass carbon nitrogen ratio (SMBC/SMBN), microbial biomass carbon to total organic carbon ratio (SMBC/TOC), and microbial biomass nitrogen to total nitrogen ratio (SMBN/TN) at different growth stages of summer maize under different fertilization measures in humid soil for 21 years, the response characteristics of soil microbial biomass carbon and nitrogen to different fertilizers were elucidated. Select 7 fertilization treatments: no fertilization (CK), single application of nitrogen fertilizer (N), balanced application of nitrogen phosphorus potassium (NPK), application of nitrogen phosphorus potassium fertilizer+organic fertilizer (NPKM), and application of nitrogen phosphorus potassium fertilizer+corn stover (NPKS). Soil samples were collected from the plow layer (0-20 cm) during the four growth stages of summer maize, including seedling stage, tasseling, grain filling, and maturity. The soil microbial biomass carbon and nitrogen were measured using chloroform fumigation method. Both NPKM and NPKS treatments can significantly increase soil microbial biomass carbon and nitrogen at different growth stages of maize, with NPKM showing the best effect. The soil microbial biomass carbon treated with NPKM increased by 36.6%, 91.7%, 167.5%, and 100.6% in the seedling stage, tasseling stage, filling stage, and maturity stage, respectively, compared to the CK treatment; The soil microbial biomass nitrogen increased by 2.0, 4.6, 3.6, and 2.5 times during the seedling stage, tasseling stage, grain filling stage, and maturity stage, respectively. At different growth stages, the soil microbial biomass carbon and nitrogen in the same fertilization treatment showed an overall increasing trend as the growth stage progressed. Compared with CK, fertilization significantly reduced the soil microbial biomass carbon nitrogen ratio; Simultaneously increasing the ratio of microbial biomass carbon to total organic carbon (SMBC/TOC) and microbial biomass nitrogen to total nitrogen (SMBN/TN), with NKPM showing the largest increase of 25.3% and 147.0%, respectively. The combined application of organic-inorganic significantly increased the microbial biomass carbon and microbial biomass nitrogen in the topsoil of summer maize at different growth stages, and the effect was better when combined with chemical fertilizers and organic fertilizers. The combination of organic-inorganic application reduces the carbon to nitrogen ratio of soil microbial biomass, increases the ratio of soil microbial biomass carbon to organic carbon and the ratio of soil microbial biomass nitrogen to total nitrogen, thereby promoting soil microbial carbon and nitrogen sequestration and improving soil carbon and nitrogen fertility.
Key Words：
long-term fertilization; corn; soil microbial biomass carbon; soil microbial biomass nitrogen; soil microbial biomass carbon nitrogen ratio
