2.6 Statistical analysis
In this study, each group (nitrogen rates and control treatments)
consisted of four physicochemical and biological replicates, and results
are shown as the mean value plus/minus standard deviation and the
statistical significance is accepted at p < 0.05. Using
SPSS Statistics 17.0 (IBM Company, Armonk, NY, USA), one-way analyses of
variance (ANOVA) and two-way ANOVA comparisons were used to identify the
effect of nitrogen rates and cultivation time on soil chemical
properties and microbial communities. Using the QIIME software 1.7.0
(https://qiime.org), the diversity indices including observed OTUs,
Chao1, ACE, Shannon, Simpson and coverage were obtained and used to
evaluate the biodiversity based upon the richness of the species and to
estimate the abundance-based richness within the community (Magurran,
2013). Based upon CANOCO version 5.0 (Microcomputer Power, Ithaca, USA),
principal coordinates analysis (PCoA) was employed to analyze the
abundance of bacterial class to visualize differences in soil bacterial
communities, and redundancy analyses (RDA) were conducted to investigate
the relationship between environmental factors and bacterial community
structure.
3. Results