Quantifying the Effect of Soil Erosion on Soil Fertility Using GIS and Remote Sensing Techniques.

Abstract

Soil erosion is a major challenge to agriculture especially in hilly and mountainous areas. The removal of top fertile denies crops access to the much needed soil nutrients thereby causing little or no yield. This study aimed at quantifying the effect of soil erosion on the spatial distribution of these nutrients in a GIS and remote sensing environment using the Revised Universal Soil Loss Equation. The RUSLE model was incorporated in a GIS and Remote sensing environment was employed to assess the amount of soil loss in the study area for the years 2000, 2010 and 2020 by evaluating the parameters of soil erosion, i.e., rainfall erosivity (R), soil erodibility (K), cover management (C) and topography (LS). The computed mean annual soil losses of the study area were found to be 25.36 t ha-1 yr-1 in 2000, 48.11 t ha-1 yr -1 in 2010 and 41.6 t ha-1 yr -1 in 2020. LS and R factors were the major soil loss contributors. Inverse Distance weighting was used to form a continuous layer from the soil nutrient point data. Basic map algebra techniques were used to obtain the amount of soil nutrients per soil loss/gain in the study area. The change in potassium content per use of soil loss/ gain experienced a 13% increase, 75% no change and a 12% decrease between study year 2000 and 2010. Between 2010 and 2020, the change of potassium content in eroded soils was 25%, 57% and 18% increase, unchanged and decreased respectively. The change in phosphorous content per use of soil loss/ gain experienced a 0.04% increase, 99.93% no change and a 0.03% decrease between study year 2000 and 2010. Between 2010 and 2020, the change of phosphorous content in eroded soils was 0.004%, 99.946% and 0.05% increase, unchanged and decreased respectively. The research realized that potassium content in the soil was more affected by soil erosion than Phosphorous. It is recommended that soil conservation practices such as terracing and afforestation should be intensified in the study area so as to reduce the amount of soil lost to downstream areas.