ABSTRACT

A greenhouse experiment was conducted to compare activated rock phosphate (APR) and a synthetic phosphorus pentoxide — P205(P) as sources of phosphorus for maize production. Two texturally contrasting soils, clay (Si) and sandyclay loam (S2) were used. The clay soil was collected from Okporo-enyi Ibere while the sandy clay loam was from western farm of Michael Okpara University of Agriculture, Umudike. Treatments included (1) control (C), (2) nitrogen and potassium (N+K), (3) nitrogen, potassium and synthetic phosphorus (N+K+P), (4) nitrogen, potassium and activated rock phosphate (N+K+APR) and (5) nitrogen, potassium, synthetic phosphorus and activated rock phosphate (N+K+P+APR). Maize was used as a test crop. The experiment was laid out as a split plot in a completely randomized design with three replications of each treatment. The two soil samples constituted the main plot treatments while the fertilizers constituted the sub plot treatment. Data collected were subjected to statistical analysis as a split plot. Analysis of Variance (ANOVA) was used to detect differences in the mean values while LSD005was used to determine the level of significant differences at 5% probability level. Results indicated a reduction in available P in all the treatments compared with the control. Although, with regard to Si and.referring to available P, synthetic P (32.6 mg/kg) was better than APR (29.3 mg/kg). However, there was no significant difference. Acidity, significantly 5 reduced with treatment application in both soils when compared to the control. Highest pH (H20) value was 6.2 in Si while it was 5.3 in S2 whereas control in Si was 4.1 and 4.3 in S2. No significant difference was observed in pH between P and APR in both soils. With respect to exchangeable calcium and sodium and referring to Si, Ca increased from 1.8 (cmol/kg) in the control to 2.5 (cmo117kg) in APR while Na decreased from 0.87 (cmol/kg) to 0. 1(cmol1ikg). Comparing P and APR, dry matter yield was better with APR in S2 though the difference was not significant. The APR performed better in S2 than in Si. Perhaps The effect was soil-specific. Therefore, APR can be recommended for use as a source of P in crop production, especially for sandy clay loam soils.