Abstract:A 2a field experiment was conducted in Qilian Grape Sightseeing Garden of Gansu Province in order to investigate the effects of biogas slurry application amount and year on soil quality and soil microbial functional diversity. The designed treatments included CK treatment (pure chemical fertilizer, N 180 kg/hm2, P2O5 150 kg/hm2, K2O 22.5 kg/hm2), biogas slurry replacing chemical fertilizer treatments (biogas slurry nitrogen replaced 33%, 67% and 100% of chemical fertilizer nitrogen), and increasing biogas slurry treatments (biogas slurry nitrogen were 133%, 167% and 200% of chemical fertilizer nitrogen). Soil microbial functional diversity was determined by Biolog method. The results showed that metabolic activity of soil microbial community was the lowest in 100% biogas slurry treatment but the highest in 33% biogas slurry treatment. Meanwhile the differences in metabolic activity between the treatments with 2a application biogas slurry were greater than those of 1a. The main carbon sources used by soil microbes were carbohydrates, biogas slurry application significantly increased the utilization rates of amino acids and carboxylic acids. Under the condition of applying biogas slurry for 2a, the effects of 133% and 167% biogas slurry treatments were better than those of other treatments. Compared with CK, biogas slurry application only had obvious advantage in promoting the McIntosh index, and the effects of 133% and 167% biogas slurry treatments were better than those of other treatments. Principal component analysis (PCA) showed that biogas slurry applying amount and year had different effects on soil microbial carbon source utilization rate and metabolic diversity, and the variation degree among treatments increased with increasing applying year of biogas slurry. Carbohydrates and amino acids were the main carbon sources that caused the differentiation of soil microbial functional groups treated with different amounts of biogas slurry, and carbohydrates were the sensitive carbon sources for soil microbial community changes after the increase of applying year of biogas slurry. Pearson correlation analysis showed that soil microbial community functional diversity had positive correlation with soil organic matter and available N, and negative correlation with available P and K. In conclusion, biogas slurry application (particularly combined with chemical fertilizer) is beneficial to improve soil microbial metabolic activity and soil microbial community functional diversity, and it can completely replace chemical fertilizer when enough amount is applied.