Determination of Appropriate Soil Test Extractant for Available Phosphorus in Southwestern Nigerian Soils

Abstract

Evaluation of five soil phosphorus (P) extractants was done on southwestern Nigerian soils from sedimentary and basement complex parent materials to determine the relationship between the extractants and the most appropriate extractant for the soils. The soils differed in properties. Generally, soils from the basement material had less available P compared with sedimentary material. Olsen extracted the greatest P. Bray 1 measured 67% of Olsen P, Hunter measured 52%, Mehlich measured 42%, and Ambic measured 24%. Positive and significant regression (P < 0.001) existed among Bray 1, Olsen, Mehlich, Hunter, and Ambic extractants. The strongest relationship was found among Olsen, Mehlich, and Ambic P. The relationship between maize P uptake and extracted P was quadratic, whereas the relationship with Mehlich was logarithmic. Bray, Mehlich, and Olsen P were the significant contributors to the maize P uptake and dry-matter yield. Extractants in order of P extraction were Olsen > Bray 1 > Hunter > Mehlich > Ambic.

Keywords:

• Nigerian soils
• phosphorus extractant
• soil test