Assessment of Soil pH and Nutrient Availability on Cocoa Farms in Cross River State, South South Nigeria

This study assesses soil pH and the availability of key macronutrients and micronutrients on smallholder cocoa farms in Cross River State, located in Nigeria's South South geopolitical zone. Cocoa is the primary cash crop in Cross River State, and soil acidity combined with nutrient imbalances are recognised as major contributors to declining cocoa yields and tree health in the state. Using a cross-sectional survey design, composite soil samples were collected from 0 to 25 cm Soil Scienceh on 35 active cocoa farms across Ikom, Akamkpa, and Obubra local government areas. Samples were analysed for pH (in water and 0.01M CaCl2), organic carbon, total nitrogen, available phosphorus, exchangeable potassium, calcium, and magnesium, and DTPA-extractable zinc, manganese, iron, and copper. Findings revealed that 77 percent of sampled cocoa farm soils had pH values below 5.0, creating conditions of aluminium and manganese toxicity and reduced phosphorus availability. Available phosphorus was critically low (below 10 mg/kg) in 69 percent of samples. Zinc deficiency was indicated by DTPA-extractable zinc below 0.5 mg/kg in 54 percent of farms. Cocoa farms with retained shade trees showed significantly higher organic carbon and calcium than shade-free farms, suggesting that shade management positively influences soil chemistry. The study recommends liming at one to two tonnes per hectare, balanced fertiliser application, and retention of shade trees as integrated soil fertility management practices for Cross River State cocoa farms. Keywords: soil pH, cocoa farms, nutrient availability, Cross River State, soil acidity.