2.3 Analysis of soil properties
The soil pH and EC were estimated in 1:2.5 soil to water suspension
(Jackson, 1973). The BD was estimated using a soil core method (Blake,
1965). Ammonium acetate extractable cations like sodium (Na), potassium
(K), calcium (Ca) and magnesium (Mg) (Hanway & Heidel, 1952) were
estimated using atomic absorption spectrophotometer (AAS) (nova400P,
Analytik Jena, Germany). The SOC was analyzed by Walkley & Black (1934)
wet oxidation method. The soil available nutrients were estimated as -
soil available nitrogen (N) by alkaline potassium permanganate method
(Asija & Subbiah, 1956) and soil available phosphorus (P) by a
colorimetric method (Bray & Kurtz, 1945). Diethylenetriaminepentaacetic
acid extractable micronutrients like iron (Fe), manganese (Mn), copper
(Cu) and zinc (Zn) (Lindsay & Norvell, 1978) were determined using AAS.
The 0.15% CaCl2 extractable sulfur (S) (Williams &
Steinbergs, 1959) and hot water-soluble boron (B) (Gupta, 1967) were
estimated using a spectrophotometer. The soil properties were tested for
normality and under the situation of non-linearity Box-Cox
transformation was used to make it normal for model development and the
model estimation were back-transformed to original units for those soil
properties for evaluation (Table 1).