2.2.3 Determination of soil physical and chemical properties
We determined soil organic matter content using the potassium dichromate
volumetric method, soil total N using the semi-micro Kjeldahl method,
soil total phosphorus (P) using the sulfuric acid perchloric acid
digestion molybdenum-antimony anti-colorimetric method, soil available P
using the molybdenum-antimony anti-colorimetric method extracted by
sodium bicarbonate, soil available potassium (K) using ammonium acetate
flame spectrophotometry, and soil alkali-hydrolyzed N using the
alkali-hydrolyzed diffusion method (Wei et al., 2014).