Effects of chicken manure mixed with inorganic fertilizer on soil enzyme activities, microbial biomass C and N at rhizosphere of poplar seedlings

Chicken manure is an important organic amendment that regulates the functional properties of agricultural systems. However, there is little information on the effect of chicken manure co-applied with inorganic fertilizer on the ecological environment at rhizosphere soil of poplar seedlings. Considering the benefits of chicken manure, a pot experiment was conducted to determine whether the chicken manure co-applied with inorganic fertilizer benefits the ecological environment of poplar seedlings rhizosphere soil. There are five treatments in the pot experiment, CK (neither urea nor chicken manure was applied), N100 (100% of nitrogen was provided by urea), M10N90 (10% and 90% of nitrogen was provided by chicken manure and urea, respectively), M30N70 (30% and 70% of nitrogen was provided by chicken manure and urea, respectively), and M50N50 (50% and 50% of nitrogen was provided by chicken manure and urea, respectively). The study was conducted to determine the effects of chicken manure co-applied with inorganic fertilizer on soil enzyme activities, soil microbial biomass carbon（SMBC）and soil microbial biomass nitrogen（SMBN）at rhizosphere soil of poplar seedlings. The results indicate that compared with the N100 treatment, regardless of the ratio between chicken manure and inorganic fertilizer, chicken manure could increase soil enzyme activities, SMBC and SMBN contents. The M30N70 treatment could increase the activities of soil urease, alkaline phosphatase, catalase and invertase by 14.41%-26.49%, 13.87%-27.93%, 12.07%-27.08%, and 29.17%-46.43%, respectively and could increase the SMBC and SMBN contents by 63.00%-76.62% and 40.01%-90.38%, respectively. The maximum activities of soil urease, alkaline phosphatase, catalase and invertase are observed on the day of 120 after fertilizers application during the experimental period, while the maximum amounts of SMBC and SMBN are observed on the day of 90 at 956.48 mg/kg and on the day of 30 at 85.39 mg/kg, respectively. Additionally, the SMBN content is decreased along with the delayed growing time of poplar seedling, but a slight increased SMBN is observed at the abscission period. Compared with the M30N70, the M10N90 and M50N50 have less effects on soil enzyme activities, SMBC and SMBN contents of one-year-old poplar seedlings. As a result, chicken manure co-applied with inorganic fertilizer, especially the M30N70 treatment, is beneficial to the ecological environment at rhizosphere soil of poplar seedlings, with the higher soil enzyme activities, soil microbial biomass carbon and soil microbial biomass nitrogen contents.