Effects of compound biofertilizer on aggregate stability and enzyme activity in tobacco-planting rhizosphere soil

【Objective】To evaluate effects of compound biofertilizer application on tobacco-planting soil quality improvement,and to provide a scientific basis for development and application of compound biofertilizer for high-quality tobacco production.【Method】A 2-year cabbage-tobacco rotation fixed micro-plot experiment was conducted for 4 seasons.Taking no fertilization group was set as control(CK) to investigate the effects of the application of inorganic compound fertilizer(CF),bio-organic fertilizer(OF),and compound biofertilizer(MF) on aggregate stability and enzyme activity in the rhizosphere tobacco-planting soil.【Result】After 4 consecutive cropping seasons,the cumulative content of water-stable aggregates>0.25 mm,mean weight diameter(MWD),and geometric mean diameter(GMD) of each fertilizer treatment increased significantly compared to those of initial soil(P<0.05,the same below),in the order of OF>CF>MF;in OF treatment,the cumulative content of water-stable aggregates>0.25 mm increased significantly by 6.8% and 14.5%,the MWD increased by 7.9% and 36.1%,and the GMD increased by 10.5% and 32.2%,respectively,compared to CF and MF treatments. According to random forest analysis,content aggregates of 2-5 mm and >5 mm were the most important factors affecting MWD and GMD. Soil urease and sucrase activity increased while soil peroxidase activity increased and then decreased in each fertilizer treatment during 4 consecutive cropping seasons;compared to CF treatment,activity of soil urease,sucrase and catalase in OF and MF treatments increased significantly in the 4^th season,with increases of 11.9%-18.4%,62.7%-129.1% and 6.7%-6.8%,respectively. Pearson correlation analysis showed that activity of 3 soil enzymes correlated positively with the content of water-stable aggregates of 2-5 mm and 1-2 mm,MWD,and GMD,while correlated negatively with the content of water-stable aggregates of 0.25-0.5 mm and <0.25 mm.【Conclusion】Compare with applying bio-organic fertilizer,applying inorganic compound fertilizer for 4 consecutive cropping seasons in 2 years could synergistically enhance the aggregate stability and enzyme activity. In addition,the application of compound biofertilizer in rhizosphere tobacco-planting soil does not obviously improve aggregate stability enzyme activity,yet significantly enhance enzyme activity.