(0.17m3m3) and ACS (0.15m3m3) than in FS (0.12m3m3). The annual
microbial biomass Cwas observed to be higher in NR (232.71mg kg−1)
and ACS (189.22 mg kg−1) than in FS (128.69 mg kg−1), and similar
trends were also observed in case of soluble carbon. A trend of higher
metabolic quotient indicates that FS has a major level of disturbance
and energy demand (Fig. 5d) compared to the other soil management
systems for all study periods. Relationship between microbial biomass
C and total organic C (microbial quotient) is leaning to be higher in FS
(1.85%) than in ACS (0.95).
3.4. Soil quality index
The selected variables (14 soil attributes previously mentioned)
were included in the PCA to determine soil quality index. The PCA generated
14 PCs. According to Kaiser criterion, the minimum number of
components to retain was equal to three as the eigenvalues started to
be lower than 1 at PC3 (Table 4). Therefore according to this criterion,
the first three PCs should be kept. Three principal components (PC1, 2
and 3) have eigenvalues N1.00 and explained 94% of the variance in
the data set (Table 4). Consequently, the first three PCs were retained
to represent the original variability of the data-set. The other components
gave a relatively small contribution to the variance. The PC1 had
seven highly weighted variables: total organic C, C and N stock, CO2–C
emission, soil temperature,microbial biomass C andmetabolic quotient.
The PC2 had one highlyweighted variable: C/N ratio. The highlyweighted
variables for the PC3 included labile and soluble C.
A correlation matrix for the highly weighted variables under different
PCs was run separately to find out redundant variables within
each PC (Table 5). The highlyweighted variables under PC1were all significantly
correlated (excepted N stock). Soil CO2–C emission, soil