Soil Phosphorus Fractions, Reaction, and Conductivity in Some Southwestern Nigerian Soils as Affected by Animal Manure Mixtures

Phosphorus fractions constitute a strong determinant of phosphorus availability in soils and their amount fluctuates with the application of manure and NPK fertilizer. Incubation study, screen house, and field experiments were conducted to evaluate the effects of animal manure mixtures on soil phosphorus fractions, pH, and electrical conductivity (EC) in some southwest Nigerian soils. Surface soil samples (0-20 cm) from four locations and cured animal manures (goat, cattle, and poultry) were collected, dried, and analyzed. Treatments of control (no manure), manure mixtures of cattle-goat, cattle-poultry, poultry-goat, and NPK 15:15:15 at 90 kg P ha(-1) were applied to soils. Samples were taken fortnightly and analyzed for pH, EC, and P fractions (Available-P, Labile-P, Aluminum-P[Al-P], and Iron-P[Fe-P], Calcium-P [Ca-P]and Residual-P). Significant (p < .05) increase in pH was observed at the onset of the experiments with subsequent decreases across weeks, a reverse trend was observed for soil EC. The addition of poultry manure complimented the effect of goat manure by increasing Labile-P, Al-P, and Fe-P, Ca-P, Residual-P while cattle-goat manure mixture increased available P. Under the field trial, a significant (p < .05) increase occurred in Labile-P, Ca-P, and Residual-P with the application of poultry-goat manure. While in available-P, Al-P, and Fe-P, poultry manure addition complimented the effect of cattle manure by significantly (p < .05) increasing the P fractions. Poultry manure inclusion is recommended for use in manure mixtures because of its complementary and synergistic effect on other manures.