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Agronomy Journal Abstract -

Comparison of Different Phosphorus Extractants in Soils of the Western State of Nigeria1


This article in AJ

  1. Vol. 66 No. 5, p. 639-642
    Received: Oct 13, 1973

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  1. Bernard F. D. Oko and
  2. Akinola A. Agboola2



Researchers in Western Nigeria have a problem in choosing a universally accepted extractant for soil test correlations. Many P extractants that are in use today have been adopted without sufficient investigation.

In the present study, 8 different P extractants were used in extracting P from 90 surface soil samples taken from 2 different ecological zones of the Western State of Nigeria. Soil P values for the different extractants before the first crop of rice (Oryxa saliva var. ‘OS6’ upland rice) were correlated with P uptake of the first crop, cumulative P uptake (P uptake for two croppings of 8 weeks each), and with cumulative yield (dry matter for two croppings). Soil P values after first crop were correlated with P uptake of the second crop.

Results suggested that different ecological zones may require different extractants, viz. Bray No. 2 (0.03 N NH4F + 0.1 N HC1) (r = 0.433*) for the swamp soils; Bray No. 4 (0.5 N NH4F + 0.1 N HC1) (r = 0.491**) for the Ikenne soils, and Bray No. 1 (0.03 N NH4F + 0.025 N HC1) (r = 0.383*) for the Ilora soils, but the general purpose extractant for rice in soils of the Western State was Bray No. 1 (r = 0.372***).

With the swamp soils, there was a negative correlation when soil P after first crop was correlated with second P uptake. The North Carolina extractant (0.05 N HC1 + 0.025 N H2SO4) (r = 0.462**) gave the best reliability for Ikenne soil. The Bray Nos. 1 and 2 were equally useful in both correlations for the above, as well as initial soil P with first P uptake although there was a slight preference in the former for the Bray No. 2 (r = 0.513**) over Bray No. 1 (r = 0.396*). For the 90 soil samples, Bray No. 2 (r = 0.279**) gave better correlation between soil P after first planting with second P uptake.

Correlation of initial soil P with one cropping of 8 weeks was better for swamp soils, whereas in Ikenne soils more confidence could be placed on correlations with second cropping and cumulative P uptake. For the Ilora soils and with a combined group (consisting of 90 soil samples) there was little or no significant difference in using either.

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