VARIATION IN SOIL PHYSICO-CHEMICAL PROPERTIES IN THREE LAND USE TYPES OF OGUN RIVER WATERSHED

Abstract

Conversion of watershed to other Land Use Types (LUTs) has implications on soil nutrients. Therefore, this study investigated the effects of three LUTs on soil physico-chemical properties of Ogun River watershed. The Ogun River watershed was stratified into Guinea Savannah (GS), Rainforest (RF) and Swamp Forest (SF) Ecological Zones (EZs). Three LUTs: Natural Forest (NF), Disturbed Forest (DF) and Farmland (FL) were purposively selected in GS: GSNF, GSDF, GSFL; RF: RFNF, RFDF, RFFL and SF: SFNF, SFDF, SFFL, respectively. Five out of sixteen plots laid along the transects lines were randomly selected in each of LUTs in the three ecological zones for soil sampling. In each of the selected plots, 5 soil samples were collected at the four corners and centre of the plot at two depths: 0-15 cm, 15-30 cm. Physico-chemical properties of soil samples were determined following standard procedures. Data were analysed using descriptive statistics and Analysis of variance (ANOVA) was used to test for differences in Physico-chemical variables of Ogun River soil samples using 3 x 3 x 2 factorial experiments. There were significant differences in Physico-chemical properties among land use types, Ecological zones and between soil depths of Ogun River watershed (P < 0.05). Soil Cation Exchange Capacity ranged from 2.37±0.01 (GSFL) to 8.50±0.04 (GSNF); Total Nitrogen increased from 0.88±0.01 (RFFL) to 4.79±0.05 (GSNF) while Soil Organic Matter ranged from 1.48±0.01 (GSFL) to 13.12±0.21 (GSNF).  It was found that continuous changes in land vegetative cover Ogun River watershed through human activities negatively affected soil physico-chemical properties. Therefore, other anthropogenic activities that will intercept nutrient cycling in the watershed ecosystem must be discouraged.