Improved Corn Yields When Humic Acid Extracted from Composted Manure Is Applied to Acid Soils with Phosphorus Fertilizer

Table 1

Soil properties of the acidic soils of Sukosari, Tanggeran, and Karangsalam, Indonesia.

Soil properties	Unit	Sukosari	Tanggeran	Karangsalam	Average
Sand	g kg^−1	1.5	13.6	2.9	6.0
Silt	g kg^−1	6.6	31.7	8.7	15.7
Clay	g kg^−1	92	54.7	88.4	78.4
pH H2O (1 : 5)		4.6	5.2	5.2	5.0
CEC	cmol^(+) kg^−1	16.7	14.3	15.8	15.6
Exchangeable K	cmol^(+) kg^−1	0.60	0.31	0.36	0.42
Exchangeable Na	cmol^(+) kg^−1	0.004	0.01	0.02	0.01
Exchangeable Ca	cmol^(+) kg^−1	2.14	2.19	2.13	2.16
Exchangeable Mg	cmol^(+) kg^−1	0.47	1.03	1.24	0.91
Available P (Bray^−1)	mg kg^−1	1.9	2.2	1.1	1.8
Exchangeable Al	cmol^(+) kg^−1	1.2	0.5	0.5	0.73