Efficiency of biochar, nitrogen addition and microbial agent amendments
in remediation of soil properties and microbial community in mine soils
Abstract
Lacking of systematic evaluations in soil quality and microbial
community recovery after different amendments addition limits
optimization of amendments combination in coal mine-soils. We performed
a short-term incubation experiment over 12 weeks to assess the effects
of three amendments (biochar: C; nitrogen fertilizer at three levels:
N-N1~N3; microbial agent at two levels:
M-M1~M2) based on C/N ratio (regulated by biochar and N
level: 35:1, 25:1, 12.5:1) on soil quality and microbial community in
the Qilian Mountains, China. Over the incubation period, soil pH and
MBC/MBN were significantly lower than unamended treatment in N addition
and C+M+N treatments, respectively. Soil organic carbon (SOC), total
nitrogen (TN), available nitrogen (AN), available phosphorus (AP),
available potassium (AK), microbial biomass carbon (MBC) and microbial
biomass nitrogen (MBN) contents had a significant increase in all
amended treatments (P<0.001). Higher AP, AK, MBC, MBN and
lower MBC/MBN were observed in N2-treated soil(corresponding to C/N
ratio of 25:1). Meanwhile, N2-treated soil significantly increased
species richness and diversity of soil bacterial community
(P<0.05). Principal coordinate analysis further showed that
soil bacterial community compositions were significantly separated by N
level. C-M-N treatments (especially at N2 and N1 levels) significantly
increased the relative abundance (>1%) of the bacterial
phyla Bacteroidetes and Firmicutes, and decreased the relative abundance
of fungal phyla Chytridiomycota (P<0.05). Redundancy analysis
illustrated the importance of soil nutrients in explaining variability
in bacteria community composition (74.73%) than fungal (35.0%). Our
results indicated that N and M addition based on biochar can improve
soil quality by neutralizing soil pH and increasing soil nutrient
contents, and the appropriate C/N ratio (25:1: biochar+N2-treated soil)
can better promote mass, richness and diversity of soil bacterial
community. Our study provided a new insight for achieving restoration of
damaged habitats by changing microbial structure, diversity and mass by
regulating C/N ratio of amendments