In order to explore the biological effect of monosodium glutamate wastewater on forest soil and determine the appropriate application level of monosodium glutamate wastewater and inorganic fertilizer for improving poplar growth

a pot experiment including five treatments

i.e. CK (neither urea nor monosodium glutamate wastewater was applied)

N100 (100% of nitrogen was provided by urea)

M10N90 (10% and 90% of nitrogen were provided by monosodium glutamate wastewater and urea

respectively)

M30N70 (30% and 70% of nitrogen were provided by monosodium glutamate wastewater and urea

respectively) and M50N50 (50% and 50% of nitrogen were provided by monosodium glutamate wastewater and urea

respectively) was performed. The present study was conducted to determine the effects of different treatments on active organic carbon

carbon pool management index (CPMI)

microbial respiration and metabolic quotient in soil

as well as growth of poplar seedlings. Results showed that in comparison with N100 treatment

monosodium glutamate wastewater application significantly increased the contents of active organic carbon

mid-active organic carbon and highly active organic carbon. The active organic carbon content and CPMI in M30N70 treatment were obviously higher than other treatments

increasing 34.78% and 42.96 compared with N100 treatment

respectively. The M30N70 treatment also significantly increased the contents of microbial biomass carbon and microbial biomass nitrogen. In the meantime

the microbial respiration was evidently enhanced by the use of M30N70 treatment

while the metabolic quotient was decreased

increasing 81.13%

35.21%

17.07% and 5.49% in microbial respiration over the treatments of CK

N100

M10N90 and M50N50

respectively. And the metabolic quotient was reduced by 9.16%

10.37%

6.98% and 5.80%

respectively. Additionally

the ground diameter and plant height in M30N70 treatment also reached the maximum and had significant differences with other treatments. However

in M10N90 and M50N50 treatments

less effect on micro-domain environment characteristics and growth was observed than that in M30N70 treatment. Correlation analysis revealed that ground diameter and plant height were significantly or extremely significantly correlated with different degree of soil active organic carbon

carbon pool management index (CPMI) and microbial activity

indicating close inner link among every indicator. These results suggested that monosodium glutamate wastewater combined with inorganic fertilizer

especially M30N70 treatment

was beneficial to increase the active organic carbon content

enhance the microbial activity in soil and promote growth of poplar seedlings.