Edosa Parker OMOROGBE

The study was carried out to investigate potassium availability in soils of an oil palm lantation invaded with different weed types in Ekasa Village, Ovia North East Local overnment area of Edo State, Nigeria. Soil samples were collected at two different depths (0-15cm and 15-30cm) with three replicates each, at four different weeds-invaded areas overing at least one acre each. The weeds investigated are; Spear grass (SR) (Imperata cylindrica), Guinea grass (GR) (Panicum maximum), White weed or goat weed (WR), Ageratum conyzoides), and Siam weed (Chromolaena odorata) (CR). The results showed that the soil of the plantation is loamy sand which is moderately acidic (mean pH value 4.67). In all the weeds investigated the potassium contents in the soils at 0-15cm depth are very low (WR=0.1724 Cmol/kg, SR=0.1008 Cmol/kg, GR=0.1838 Cmol/kg, and 0.1478 Cmol/kg) and these values are reducing with increasing depth. At both 0-5cm and 15 – 30cm depth, there are no significant differences in the potassium contents mong the soils of all the weeds investigated. The portions with CR and GR have high and significantly same organic carbon contents at 0-15cm (23.61g/kg and 23.01g/kg respectively) but moderate organic carbon content at 15-30cm (18.22g/kg and15.23g/kg respectively) which are also significantly the same, while the portions with WR and SR have moderate organic carbon contents at both depths (15.49g/kg, .91g/kg and 42g/kg, 14.76g/kg respectively). The Organic carbon content in the CR portion was the highest (23.61g/kg) followed by the portion with GR (23.01g/kg) at 0-15 cm depth while the ortion with WR is the lowest (15.49g/kg). The 15-30cm depths also followed the same end. There was a significant difference between the mean value of organic carbon content of the portion with WR (15.49g/kg) and CR (23.61g/kg). There were no significant differences between the nitrogen value in soils of CR and GR at both depths. The results also showed that the soils of the portion with CR has significantly the highest nutrients reserve of followed by GR, then SR while WR has the lowest fertility levels.