LAUSR

ABSTRACT Iron-impregnated filter paper (Fe-Pi) was evaluated as phosphorus (P) extractant in four soils of Ogun state, southwest Nigeria in a screenhouse experiment. The experiments lasted for 8 weeks. Soil P contents were extracted at 0, 4, and 8 weeks after the incorporation of amendments (cattle manure, poultry manure, and wood ash) using Fe-Pi, Bray-1, Bray-2, Mehlich-1, Hunter, and Olsen extractant. Agronomic variables were taken fortnightly from grown maize plants and later harvested at 8 weeks, residual effects of the treatments were also evaluated. Maize dry matter weight (DMW) and P uptake were also measured. Results indicated that a linear relationship existed among the extractants with significant coefficient at p ≤ .001. Fe-Pi established a strong relationship with the conventional extractants in the following order: Bray-1 (R 2 = 0.99) > Bray-2 (R 2 = 0.98) > Hunter (R 2 = 0.96) > Mehlich-1 (R 2 = 0.86) > Olsen (R2 = 0.82). Fe-Pi had a significant relationship with P uptake and DMW. Phosphorus uptakes under the animal manure amendments were statistically higher than uptake in control and woodash amended soils. Therefore, the study concluded that Fe-Pi was a good predictor of plant available P and had significant relationship with Bray-1, thus it could be considered for the estimation of soil available P in soils of southwest Nigeria.