Comparison of Selected Extractants for the Estimation of Available K in Soils of Edo State of Central Southern Nigeria

Comparison of five selected extractants for estimation of available K in soils of Edo State of Central Southern Nigeria was carried out in a greenhouse with maize as the test crop. The five extractants used were distilled water, 0.5 N NaHCO₃ (pH 8.5), 0.01 M CaCl₂, 0.1 N HNO3 and 1 N NH₄OAc (pH 7). Nine composite surface (0-15 cm depth) and subsurface (15-30 cm depth) soil samples were used in this study. The amount of extractable K by 1 N NH₄OAc (pH 7) and 0.1 N HNO₃ showed the highest significant linear correlation with K uptake and dry matter yield with 'r' values of 0.910***, 0.895*** and 0.718***, 0.754*** (P = 0.001) respectively, when compared with distilled water, 0.5 N NaHCO₃ (pH 8.5) and 0.01 M CaCl₂. The use of 1 N NH₄OAc (pH 7) and 0.1N HNO₃ soil tests could be recommended because they appeared to have almost equal efficiency in terms of the ability of extracting available K from these soils.

Keywords: available K; Central Southern Nigeria; Edo State soils; extractants

DOI: 10.4038/tare.v10i0.1876

Tropical Agricultural Research & Extension Vol.10 2007 83-87