Effectiveness of Extractants for Bioavailable Phosphorus in Tropical Soils Amended with Sewage Sludge

Table 5

Mean of phosphorus concentrations extracted by Mehlich-I, H₂SO₄, and resin from samples collected at three depths from soils treated with varying rates of sewage sludge and composted sewage sludge, in the short-term experiment ().

Rates	Mehlich-I	H2SO4	Resin
	mg kg^−1
	0–10 cm
0	8.4^a	7.1^a	12.3^a
50	13.5^a	11.0^a	18.0^a
100	8.8^a	7.2^a	11.9^a
200	10.2^a	8.4^a	12.1^a
RL	ns	ns	ns
RQ	ns	ns	ns
	10–20 cm
0	5.5^a	4.4^a	4.9^a
50	7.2^a	5.8^a	8.5^a
100	6.6^a	5.4^a	7.1^a
200	7.1^a	5.9^a	9.5^a
RL	ns	ns	ns
RQ	ns	ns	ns
	20–40 cm
0	7.0^a	6.1^a	7.9^a
50	3.8^a	3.3^a	4.2^a
100	5.1^a	4.5^a	5.4^a
200	3.2^a	2.1^a	6.5^a
RL	ns	ns	ns
RQ	ns	ns	ns

RL: linear regression; RQ: quadratic regression; ns: not significant at 5%.
^**Values with the same letter within a column in the same depth are not different (Tukey, ).