Abstract: To reveal the effect of vegetables waste in situ returning on soil microbial function in the next season, the field experiment was carried out to research the effect of vegetables waste in situ returning on soil available carbon and nitrogen, and microbial carbon source utilization capacity. Three treatments set as follow： Conventional fertilization without returning（CK）, conventional fertilization with vegetables waste returning （FS） and conventional fertilization reduced by 30% with vegetables waste returning （FS-30N）. The results showed that compared with CK, within 60 days, the content of FS and FS-30N treatments on soil nitrate nitrogen increased by 6.51%~21.18% and 3.79%~18.99%, respectively, but the content of soil active organic carbon and the ability of soil carbon source utilization decreased. The diversity of soil microbial function changed significantly after the application, but the difference between the three treatments decreased after 60 days. Within 60 days, the utilization ability of carbohydrates and carboxylic acids of soil microorganisms was highest. Effect of carbohydrate and polymer metabolism of nitrate nitrogen was much more than that of active organic carbon. The carbon sources showed the greatest impact on the shannon diversity index（H）, and the least impact was obtained by average degree index（E）. Microbial functional diversity was most influenced by polymers, carbohydrates and amino acids all of carbon sources. Therefore, in situ returning of Brassica campestris L. reduced the soil microbial carbon source utilization capacity and functional diversity in a short period, but the decreasing trend was slowed down in the later period （60 days）, and the effect of 30% reduction of chemical fertilizer was much more than others.

Key words: activated carbon and nitrogen, carbon source utilization capacity, principal component analysis, diversity index