2.4. Statistical analysis
The SPSS16.0 (2001) software was used for descriptive statistical and
correlation analysis. Pearson product moment correlation test was
applied to assess the relationship among the soil variables. The
sampling adequacy of individual and set variables were computed by using
Kaiser-Meyer-Olkin test (>0.5) and Bartlett’s test of
sphericity (P <0.05). The PCA was computed to derive the
most identical soil indicators. To assess the long-term sugarcane
monocropping impact, two approaches were employed. First, the percentage
alter in the individual soil fertility parameters under different cane
producing zones of Uttar Pradesh to assess whether soil fertility
parameters were declines or improve. Second, Nutrient Index (NI) was
calculated using parameters following the Ramamurthy & Bajaj (1969)
approach. A Nutrient Index is an estimate of the % distribution of soil
samples across categories: low, medium and high classes of nutrient
status as per the soil test value interpretation (Amara et al., 2017) by
using: Nutrient Index (NI) = [(NL × 1) +
(NM × 2) + (NH ×
3)/NT]
where, ‘NL’, ‘NM’ and
‘NH’ typify the number of samples falling in the low,
medium and high class of nutrient status, respectively, and
‘NT’ is the total number of samples analyzed across the
cane producing zones of Uttar Pradesh. The NI levels were computed
according to low (<1.67), medium (1.67-2.33) and high
(>2.33) category. Maps showing geographical locations of
the soil sampling site were created through Google map.