Effects of Fallow Genealogical Cycles on the Build-up of Nutrients in Soils of the Cross River Rainforest, South-Southern Nigeria

Abstract

The study examined the effect of fallow generational cycles on the buildup of nutrients in the soil. Fallow sequence of 1st, 2nd, 3rd, 4th and 5th generations were studied. The quadrat approach of sampling was employed to collect soil samples (surface and subsurface) from five plots of 10m x 10m across the five fallow generational cycles. Result showed that the mean proportions of organic matter (OM), total nitrogen (TN), cation exchange capacity (CEC) and available phosphorus (Av. P) increased substantially in the 1st and 2nd generation of fallows probably due to reduced cropping frequency. The PCA result further revealed that topsoil available phosphorus, topsoil exchangeable sodium and topsoil exchangeable potassium constituted the most significant soil properties that progressively increased across the fallow generations. As usual, nutrients in the fallow generations were confined to the topsoil. The increase in soil nutrients was attributed to the increased in tree size, vegetation cover and adequate ground cover which helped to conserve and build-up essential nutrients in the soil by minimizing the loss of nutrients through soil erosion. The study suggested that for efficient conservation practices, fallow land mostly the 1st generation fallow which was fast approaching climax should be considered for reserve. For this to be feasible, alternative means of livelihoods should be provided to reduce the wanton destruction, concentration and dependence on forest resources for sustenance.

Keywords:  Fallow Genealogy, Vegetation Development, Soil, Physical Property, Chemical property, Disturbance frequency