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

Table 2

Humic acid extracted from the composted manure (MHA) combined with phosphorus (P) fertilizer treatment effects on soil chemical properties 15 weeks after planting for two corn cultivars.

Treatments	pH H2O	Exchangeable aluminum (cmol^(+) kg^−1)	Available P (mg kg^−1)
C factor
CB	5.45 q	0.63 q	3.63 q
CP	5.42 q	0.83 q	2.52 q
F factor
H0P0	5.49 a	0.98 ab	1.22 b
H0P1	5.26 a	0.56 ab	7.05 a
H5P1	5.40 a	1.11 a	3.18 ab
H10P1	5.28 a	0.88 ab	1.47 b
H15P1	5.16 a	0.11 b	2.46 ab
C × F	(—)	(—)	(—)
CV	5.41	26.13	34.96

CV is the coefficient of variation. C factor is the type of corn cultivar. F factor is a combination of MHA and P fertilizer. CB is Bisi 2 hybrid corn, CP is Pioneer 35 hybrid corn. H₀P₀ is the control, H₀P₁ is 0 mg kg⁻¹ MHA + P fertilizer, H₅P₁ is combined 35 mg kg⁻¹ MHA + P fertilizer, H₁₀P₁ is combined 75 mg kg⁻¹ MHA + P fertilizer, H₁₅P₁ is combined 110 mg kg⁻¹ MHA + P fertilizer. The rate of P fertilizer in each P₁ treatment was equivalent to 120 mg P₂O₅ kg⁻¹ air-dried soil. Values followed by the same lowercase letter in a column were not significantly different based on Duncan’s multiple range test at . The results presented are the mean of 3 replicates.