Extractable Al and Soil Solution Ionic Concentrations in Strongly Leached Soils from Northwest Iberia: Effects of Liming

Table 4

Correlation coefficient matrix (r) between the amounts of Al extracted by different extractants, and values of cation exchange capacity (CEC), and content of clay, total organic C (SOC), aluminium and iron by acidified ammonium oxalate (Alo and Feo) and by sodium pyrophosphate (Alp and Fep) in studied soils. Symbol: *, **, *** significant at the 0.001, 0.01, and 0.05 probability (𝑃) levels, respectively.

Extractants				r, 𝑃
	Soil constituents
	CEC	clay	SOC	Alo	Alp	Feo	Fep
All horizons
1 M KCl	0.80***	ns	0.70***	0.62***	0.71***	0.74***	0.79***
0.33 M LaCl3	ns	0.46*	ns	ns	ns	ns	0.48*
0.5 M CuCl2	0.85***	ns	0.69***	0.84***	0.89***	0.72***	0.78***
Surface horizons
1 M KCl	0.80**	0.66*	0.83***	0.74**	0.85***	0.77**	0.83**
0.33 M LaCl3	0.66*	0.63*	0.72**	0.60**	0.73**	0.66*	0.81**
0.5 M CuCl2	0.68*	0.61*	0.79**	0.85***	0.88***	0.71**	0.75**
Subsurface horizons
1 M KCl	0.83**	ns	0.68*	0.54*	0.65*	0.76**	0.78**
0.33 M LaCl3	ns	ns	ns	ns	ns	ns	ns
0.5 M CuCl2	0.96***	ns	0.83***	0.84**	0.92***	0.86**	0.90***