2.3 Soil basic physiochemical properties
The soil bulk density was calculated as the ratio of the oven-dried (105
°C) soil mass to the volume of the cylinder. The soil pH was determined
in a soil-to-water mass ratio of 1:2.5, and particle size by the United
States Department of Agriculture (USDA) were measured using the
gravimetric method. The soil organic matter was analysed using the
Walkley-Black potassium dichromate sulfuric acid oxidation method
(Nelson and Sommers, 1982). The total N was measured using the
semimicro-Kjeldahl method after complete digestion in
CuSO4-K2SO4-Se
(100:10:1) at 400 °C (Bremner and Mulvaney, 1982), and available N was
determined using NaOH-hydrolysation reduction-diffusion (Lu, 2000). The
total P and available P were
measured using the colorimetric molybdenum blue method via
HNO3-HClO4-HF digestion and 0.5 mol
L−1 NaHCO3 (pH = 8.5) extraction,
respectively (Murphy and Riley 1962; Olsen et al. 1954; Thomas et al.
1967). The basic soil physiochemical properties are listed in Table 3.