3.1 Descriptive statistics of the soil properties
Descriptive statistics of the properties of SAS are presented in Table
1. For the full dataset, the coefficient of variation varied from
16.75-118.30% with the highest observed for Fe (118.30%) and lowest
for soil pH (16.75%). For the calibration and validation dataset
coefficient of variation varied from 18.46 to 122.91% and 15.44 to
110.85%, respectively. The highest coefficient of variation (%) was
recorded for Fe (122.91%) and lowest for soil pH (18.46%) for the
calibration dataset whereas in the case of validation dataset it was
highest for Mn (110.85%) and lowest for soil pH (15.44%). The soil pH
and EC of the full dataset varied from 3.47-8.04 (mean 5.42) and
0.10-24.11 (mean 6.91) dS m-1, respectively. It
indicates co-existence of the salinity and acidity which is the unique
property of these soil . The SOC ranged from 0.02% to 3.20% with a CV
of 56%. A physical property, BD, varied between 0.89-2.17 Mg
m-3 with an average of 1.44 Mg m-3and CV of 18.56%. The variability with respect to the macronutrient
elements N and P was 42.76% and 93.00%. The cations, K, Na, Ca and Mg
had coefficient of variation ranging from 65.97% to 83.44%. The
variability of the micronutrients (Fe, Mn, Cu, Zn and B) varied from
63.93% to 118.30%. The results of the descriptive statistics revealed
presence of adequate variability in most of the parameters measured. All
the soil properties were positively skewed for full, calibration (except
pH) and validation dataset. To ensure the random selection of
calibration and validation dataset, test of equal means, variance,
distribution and coefficient of variation was carried out and the
results are presented in Table 2. The results of all the test were
non-significant (p ≥ 0.06) except F-test (equal variance) for S
(p=0.05) and Zn (p=0.00004). This indicates that the calibration and
validation dataset effectively represent the variability existed in the
full dataset.