Estimating Lime Equivalence of Animal Manure Ashes and Soil Reaction Kinetics in Southwestern Nigerian Soils: An Incubation Study

In this study, the liming equivalence (LE) of manures and soil pH kinetics were computed in triplicates, for soil pH measurements after eight weeks of soil incubation using manure ashes and CaCO3. The liming effects of CaCO3 and manure ashes are related to their Ca content. The pHKCl was more reliable for estimating the LE of the soil. The average LE was 0.73, 0.30, 0.26 for goat, cattle, and poultry ashes, respectively in pH KCl and 0.22, -0.22 and 0.15 in pHwater. Generally, the estimated LE of the ashes was 0.58 in pH KCl and 0.46 in pHwater. The goat manure ash had an LE value of 0.57, followed by the poultry manure ash value of (0.48); the least LE value (0.39) was found by the cattle manure ash. In alluvial soil, pH kinetics was best described by the power- function model (pHKCl), while first-order and power-function models were most appropriate for soils amended with the poultry and cattle manure ash, respectively in pHwater. In a sedimentary soil, no single kinetics model could be used to describe the changes in soil pH. The liming equivalence of the ashes was (0.58) in pHKCl and (0.46) in pHwater. Their liming equivalences relative to CaCO3 were 57, 48 and 39 %, for goat, poultry and cattle manure ash, respectively. Conformity of the soils to the kinetics model is a function of the solution (electrolyte) used for the pH estimation.