3.2 Relationship between microbial communities and soil
properties
SOC content and available N decreased with soil depth (Table 2,P <0.05). Compared to that of the control, NPK +ST and
NPK +OM showed significantly higher SOC contents at soil each depth. NPK
addition alone resulted in lower SOC content at 0–10 cm compared to
that in the control. In contrast, soil pH exhibited the opposite pattern
of SOC, which was significantly increased with soil depth, with the
highest value observed in the control (Table 2,P <0.05).
MBC and MBN decreased with soil depth in all treatments (Table 2,P <0.05). Compared to those in the control, NPK and NPK+
OM significantly increased MBC and MBN at0–40 cm, except for 10–20 cm
in NPK. In contrast, NPK + ST significantly increased MBC at0–30 cm
compared to that in the control (P <0.05). Compared to
those under NPK addition alone, the NPK + ST treatment increased MBC and
MBN at 10–30 cm and 0–30 cm, respectively; NPK+ OM treatments showed
significantly higher MBC and MBN at 0–40 cm (Table 2,P <0.05).
The RDA showed that SOC significantly contributed to the soil microbial
communities and explained 87% of the variance in the first two axes
(Figure 3a, P <0.001). Soil pH was also significantly
correlated with the microbial communities and explained 3.7% of the
total variation. Available N and SOC contributed significantly to the
microbial communities at both the 0–20 and 20–40 cm soil depths and
explained 79.3% and 4.5%, and 3.1% and 86.4% of the total variation
for each depth, respectively (P <0.05). Soil pH only
showed a significant correlation to the microbial communities at the
0–20 cm soil depths and explained 4.9% of total the variation
(P <0.013) (Figures3b and c).
DISCUSSION