Research Article
Adelabu GN, Oderhohwo KJ
Abstract
Kola nut is an economically important indigenous cash crop. Two species– cola nitida and Cola acuminata are the most prevalent in Nigeria. Soils of five Kola nut plantations in different Local Government Areas (LGAs) in Ogun State were evaluated for effects of previous farming practices as well as their suitability for continuous use for kola cultivation. The sites were selected based on production outputs from the 10 Kola nut producing LGAs in the state. The stratified random technique at depths of 0-15cm, 15 – 30cm and 30 – 45cm was employed for soil sampling. Analytical results showed the pH of the soils to be between 5.29 and 7.57, sand content between 49.95% (Mamu) and 73.57% (Agoro) and clay contents between 17.57% (Odogbolu LGA) to 35.81% (Ijebu-North LGA). The silt contents ranged from 2.64%. (Ikenne LGA) and 14.72% (Ijebu North LGA). The predominant soil texture in these areas is sandy loamy. Soil organic carbon contents were adequate in all LGAs except Odogbolu LGA which was found to be below critical levels. Odogbolu LGA was also found to have Nitrogen (N) content below the critical level for the cultivation of kola. Available Phosphorus, P in the all five LGAs was between 8.03mg/kb and 13.98mg/kg which are above the critical required value of 3.7mg/kg soil. Exchangeable Potassium ranged from 0.08cmol/kg in Ikenne LGA to 0.44cmol/kg in Sagamu LGA. The Magnesium, Mg contents of the soils in all five LGAs were found to be below the critical level. The results confirm the fact that Kola plantations thrive under different soil conditions in the state hence soil management practices have to be established specifically for each farm for maximum yields. There is no one-fits-all remedy for the farms. Coppicing of old and expired trees would also help in achieving better productivity.