Effect of Nypa Fruticans and Mangrove Species on Soil Properties in Eastern Obolo, Akwa Ibom State

The study was conducted to evaluate the effect of nypa and mangrove on soil properties to determine whether nypa in displacing mangrove was degrading or aggrading the underlying soil, in Okorombokho Community in Eastern Obolo Area of Akwa Ibom State. The study was carried out in three contiguous loca- tions, namely, mangrove (M) forest, nypa and mangrove (N&M) forest, and bare plot with neither mangrove nor nypa as control (C). In each location, undisturbed and bulk soil samples were collected from the 0-15 cm and 15-30 cm depth at 20 m intervals along a 60-m transect, for soil physical and chemical properties and micronutrients concentrations. The result showed that among the particle-size fractions, sand was significantly (p<0.05) greater in the 0-15 cm than 15-30 cm depth. Soil texture was sandy loam in N.M., M, and C. Soil density was signifi- cantly (p<0.01) higher in C (1.64 Mg m-3) than in M (1.54 Mg m-3) andN&M (1.52 Mg/m3), while 0-15 cm and 15-30 cm were similar. Saturated hydraulic conductivity was significantly (p<0.01) greater inN&M (6.04 cm h-1)by 66.4% than C 3.63 cm h-1; M (5.17 cm h-1) andN&M, and M and C were similar, but M was greater than C by 42.4%;0-15 cm (5.44 cmh-1) and 15-30 cm (4.45 cmh-1) soil depths were similar in Ksat. Soil pHwas significantly (p<0.05) higher in C than M andN&M, and also, higher (p<0.01) in 15-30 cm than 0-15 cm soil depth.The ECEC was significantly (p<0.05) greater in N&M (14.93 cmol kg-1) and C (13.74 cmol kg-1) than M (12.07 cmol kg-1); C and M and C and N&M were not statistically different. It was also greater (p<0.01) in 0-15 cm (14.23 cmolkg-1) than 15-30 cm (12.73 cmolkg-1) depth. Concentrations of Cu, Zn, Mn and Fe were generally low and lower than their permissible limits in the soil envi- ronment. Because the soil was neither aggrading nor degrading, it could be said that the invasion and virtual elimination of the native mangrove by nypa did not have an adverse impact on the physical and chemical fertility status of the soil and would, favour the regeneration of the native mangrove ecosystem.