Assessment of Soil pH and Its Effect on Nutrient Availability in Cocoa Farms in Ondo State

This study assesses soil pH variability and its effect on nutrient availability in cocoa farms in Ondo State, South West Nigeria. Ondo State is Nigeria's leading cocoa-producing state, and maintaining soil pH within the optimal range for cocoa growth, typically 5.5 to 6.5, is a fundamental agronomic requirement for high productivity. Soil acidification from continuous cropping, nutrient depletion, and the leaching effects of high rainfall is a progressive problem in many Ondo cocoa farms, but its agronomic consequences are poorly understood at the farm level. This study collects soil samples from 45 cocoa farms across Ondo West, Idanre, and Owo local government areas at 0 to 20 and 20 to 40 centimetre depths, analysing soil pH, available phosphorus, exchangeable cations, organic matter, and micronutrients. Cocoa pod yield data are recorded from sampled farms. Correlation analysis relates soil pH to nutrient availability parameters and yield. Findings reveal that soil pH in sampled farms ranges from 4.2 to 6.8, with 58 percent of farms showing pH below the optimal minimum of 5.5. Below pH 5.0, aluminium and manganese toxicity indicators are elevated, and phosphorus availability declines precipitously. A significant positive correlation is observed between soil pH within the 5.5 to 6.5 range and cocoa pod yield. The study concludes that soil acidification is a widespread agronomic problem in Ondo cocoa farms. It recommends liming programmes integrated with cocoa rehabilitation extension services.

Keywords: soil pH, cocoa yield, nutrient availability, soil acidification, Ondo State.