Determining Critical Soil pH for Sunflower Production

Table 1

Initial soil fertility conditions at Perkins, Haskell, and Lahoma, Oklahoma. Soil fertility is characterized by extractable sodium (Na), potassium (K), calcium (Ca), magnesium (Mg), aluminum (Al_KCl), effective cation exchange capacity (ECEC), and aluminum saturation (Al_sat).

Location	Na	K	Ca	Mg	AlKCl	ECEC	Alsat
	mg kg^−1					cmolc kg^−1	%
Perkins	11	37	17	5	0.9	0.28	1.3
Haskell	25	9	26	4	29.4	0.62	31.5
Lahoma	20	13	62	29	0.1	0.67	0.1