Soil Organic Carbon Dynamics under Different Plantation Crops of Different Ages in a Tropical Oxic Paleustalf

Increasing the carbon sequestration potential of the soil is one of the ways to address the increasing build-up of greenhouse gases especially carbon dioxide. A study was conducted to assess the organic carbon pool under Young and Old tree plantations at Uhonmora, Edo State, Nigeria. The plantation species included Anacadium occidentales, Theobroma cacao and Coffea robusta. Result showed that SOC pool was the maximum in the old cashew plots (45 years) and decreased in the following order SOC in young cocoa (1 year) > young coffee (6 years)> old cocoa (46 years) > young cashew (2 years) > old coffee (20 years). Results also indicated that differences in SOC pool under different plantation were statistically significant (p ≤ 0.05). The A. Occidentals plot had 6.36g/kg soil organic carbon after 45 years in this study and it was found to store more than double SOC pool when compared to other plantations. The soils also vary in the N contents. The young cashew plot was low in N content but adequate for other plots. Using the SOC as indicator, the soil organic matter content needs to be improved upon for sustainable productivity. Soil texture in all the plantations was loamy sand. Soil organic carbon content variation across the plantations with age of establishment will necessitate the need to produce a suitable habitat for microorganisms which are involved in litter degradation process. However, there was strong correlation between soil organic carbon and nitrogen (r=0.96; p≤ 0.05) across the plantations. Prediction of soil organic carbon in any of the plantation was indicated by the linear regression study.Keywords: Soil Organic Carbon, Plantation Crops, Different Ages, Tropics, Cashew, Oxic Paleustal