Comparison of selected extractants for the estimation of available K in soils of edo state of central southern Nigeria

Abstract

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.