Table 2.

Analysis method of soil variables.

Soil variable	Abbreviation	Method	Reference
Soil thickness	ST	/	/
pH	pH	pH-meter method (soil: water ratio 1:2.5)	(Page et al., 1982)
Electrical conductivity	EC	Conductivity method (soil: water ratio 1:5)	(Page et al., 1982)
Cation exchange capacity	CEC	Hexamminecobalt trichloride solution-Spectrophotometric method	(Ranger et al., 1990)
Soil total organic carbon	SOC	Wet digestion method	(Nelson and Sommer, 1975)
Soil organic matter	SOM	Potassium dichromate volumetric method	(Claudio et al., 1991)
Dry matter content	DMC	Time Domain Reflection method
Total nitrogen	TN	Kjeldahl method	(Bremner and Mulvaney, 1982)
Total phosphorus	TP	Mo-Sb colorimetric method (Involving digestion of soil samples with perchloric acid)	(Yuan and Lavkulich, 1995)
Total potassium	TK	Flame spectrometry method (Involving preliminary nitric acid digestion followed by a hydrochloric acid solubilization)	(Silva et al., 1999)