An attempt to evaluate phosphorus fertilizer requirements of western Nigeria savannah soils |
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Authors: | Olufemi Ayodele Akinola Agboola |
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Affiliation: | (1) Department of Agronomy, University of Ibadan, Nigeria;(2) Present address: National Horticultural Research Institute, PMB 5432, Idi-Ishin, Ibadan, Nigeria |
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Abstract: | A greenhouse fertilizer trial was carried out on 60 surface soils of the western Nigeria savannah derived from basement complex rocks. Bray's P1 available P in the soils varied between 1 and 112µg ml–1. There was maize response to P addition and a critical P level of 12.7µg ml–1 was calculated for the soils.For 22 of the soils, a laboratory incubation technique was used in evaluating changes in Bray's P1 extractable P at various rates with time. The initial rapid decline in soil available P was completed between 28 and 84 days of incubation. A fertilizer factor, calculated from extracted P in treated and untreated soils varied between 1.5 and 16.7µg ml–1 and was significantly correlated with soil pH and citrate-dithioniteextractable oxides of Fe and Al.Fertilizer rates based on critical soil P, available soil P and fertilizer factor, correlated significantly with greenhouse estimates for optimum yield obtained with the linear response plateau model (r = 0.91,p < 0.001). At ten field locations varying in available P content, response was only to P applications lower than 60 kg ha–1 and the calculated P rates using a mean fertilizer factor of 3.0µg ml–1 corresponded to P rates at which maximum yields were obtained in the sites. |
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Keywords: | critical P level fertilizer factor optimum yield P fixation |
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