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Akpan
US
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Determination of phosphorus fixing capacities and residual values of soils of Akwa Ibom State, Nigeria |
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1Ukpong I. M., 1Osodeke V. E. and 2*Akpan U. S. |
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1Department
of Soil Science and Met. Michael Okpara University of
Agriculture, Umudike, Abia State, Nigeria Accepted August 26, 2014 |
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Abstract |
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This study was
conducted to evaluate phosphorus fixing capacities and residual
values in soils of Akwa Ibom state, for effective and efficient
P fertilizer recommendation. Soil samples were collected based
on parent material in the study area (coastal plain sands, beach
ridge sands, sandstone/shale, and river alluvium). In each of
the parent material, soil sample were collected from three
representative locations at a depth of 0-20cm with the aid of
soil auger. A total of 12 soil samples were generated for
analysis. Treatment solutions containing 0, 20, 40, 80 and 160
mg/l were prepared from KH2PO4. 20 ml
portions of the treatment solutions were added to 20g of the
soil samples in a cup and mixed thoroughly for effective mixing
of the phosphorus solution with the soil and allowed to dry. The
cups were carefully covered and allowed to stand for 1, 7, 30,
90 and 180 days respectively. The soil samples were kept moist
with deionized water at weekly intervals and covered for the
duration of incubation. At the set days, 20 ml of Bray P-I
extractant was used to extract plant available phosphorus in the
soil samples. The phosphorus in the extract was determined using
the Murphy and Riley method (1962). The study revealed that the
mean organic matter contents in the study areas were as follows:
Fresh river alluvium (4.5%) > coastal plain sand (3.0%) >
sandstone/shale (2.0%) > beach ridge sands (1.9%). Mean clay
content was as follows: Fresh river alluvium (13.15%) > coastal
plain sand (9.82) > sandstone/shale (7.80%) > beach ridge sands
(4.87%). Mean soil pH in KCl were as follows: Fresh river
alluvium (5.1) < beach ridge sands (5.2) < sandstone/shale (5.3)
< coastal plain sand (5.4). The amount of P recovered at
different incubation periods increased with increasing level of
P addition. The proportion of added P recovered declined with
increase in incubation period in all the soil types in the study
area. Soils of fresh river alluvium had the highest P fixing
ability while breach ridge sands soil had the lowest fixing
ability. The trend is as follows: fresh river alluvium > coastal
plain sand soils > sandstone/shale > beach ridge sand soils.
Sandstone/shale soils had the highest residual values of added P
(1.1 mg/kg) while beach ridge sands soils had the lowest
residual values (0.6 mg/kg). The trend is as follows: sandstone
/shale (1.1) > coastal plain sands soils (0.9) > fresh alluvium
(0.7) > breach ridge sands soils (0.6). Split application of P
fertilizer is recommended for soils in the study area because of
formation of non-available form of P with long period of
incubation. |
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