3.1 Soil chemical and microbial properties
Temporal changes of soil chemical and microbial properties across all
the treatments are presented in Table 4 and Figure 2, respectively.
Compared with control treatment (CK), consecutive N fertilization
significantly increased SOC, TN, MBC, MBN, CMR, NMR and PRN, whereas
significantly decreased soil ECe. The effect of N
fertilization rates on soil pH, CEC and AN was not significant across
all the treatments. Soil AP showed temporal decrease trend since calcium
superphosphate was applied as soil amendment and phosphorus fertilizer
supply for single use prior to the first paddy rice season. Table 5
shows the Pearson correlation coefficient among the soil chemical and
microbial properties. Soil ECe was negatively correlated
with SOC, CEC, AP, MBC, MBN, CMR, NMR and PNR, and SOC showed positive
correlation with CEC, TN, AN, MBC, MBN, CMR, NMR and PNR. Soil microbial
properties were relevant to each other whereas the correlation between
pH and other soil attributes was not significant. The two-way ANOVA
results across all the treatments are also presented in Table 5.
Cultivation time effect of treatments on ECe, pH, SOC,
CEC, AP, MBC, MBN, CMR, NMR and PRN was observed, and the effect of N
fertilization rates on SOC, TN, AN, AP, MBC, MBN and NMR was
significant. Cultivation time and N fertilization rates had interactive
effect on AN, MBC and NMR in this study.
Table 4
Table 5
Figure 2