Spatial Analysis of Soil Fertility Using Geographical Information Systems Technology

Abstract

The research evaluated soil fertility condition of River Otamiri watershed in southeastern Nigeria in relation to topographic heterogeneity using GIS technique. GPS was used to determine the geodetic coordinate of the sampling points and site elevation. Soil samples were collected and analyzed using standard soil analysis method to determine major soil fertility parameters including soil pH, organic carbon, effective cation exchange capacity, soil particles distribution, total nitrogen and available phosphorus. These parameters were evaluated and spatially interpolated to determine its variation along topographic positions using ArcView 3.2a. The results showed that the area is dominated by sandy soil with a little percentage of clay and silt. The area is acidic with pH as 4.67 � 5.6 for the upper and lower layers and5.6 � 5.5 at crest and valley bottom and lower at the midslope. The study also showed low organic carbon [0.118 � 1.735%], ECEC [0.676 � 3.764 meq/100g for upper soil layer, 5.34 � 4.27 meq/100g for lower soil layer and lower at the midslope ], low total nitrogen concentration range of 0.008 � 0.068% and 0.018 � 0.048% for upper and lower soil layers. Total nitrogen decreased with depth. This suggests that the fertility condition of the soil may not support crops that do not survive in acidic soil. Hence, to widen the range of species that can be planted in this watershed, proper management practices to maximize nutrient cycling and nutrient use efficiency should be employed.