Abstract

Poor knowledge of soil suitability for agricultural production constitutes a major problem to land users. For proper assessment of the distribution soil properties, the use of geographic information system (GIS) has been considered a very effective tool to achieve this. A study on an Alfisol at the Institute of Agricultural Research and Training, Ibadan (7°23êž‹N, 3° 51^êž‹E), Nigeria, was carried out to measure the spatial variation of soil properties of a continuously cultivated land under rain-fed and irrigation systems. The study involved a systematic grid mapping of about 3 ha of an experimental plot subjected to maize cultivation for more than 15 years. This study area was divided into 20 m by 20 m grids, and samples were collected at each grid point for laboratory analysis while the coordinates of each sampling point was taken for interpolation in ArcGIS. The results obtained from the analysis of various elements were imported into GIS environment and then presented in form of digital maps that shows the spatial distribution of the soil properties, which can be used for precision agriculture. The results obtained showed that the area had medium acid in majority of the area covered with a pH range of 5.5 to 5.9. The %N was majorly low at < 0.08%, the organic matter content ranges between 0.4 and 3.0%, the ECEC was found to be low at < 4 cmol/kg, potassium was medium at 0.2 to 0.5 while the phosphorus content was also low having < 7 ppm. The results showed that the fertility of the area is not so high with majority of the nutrients having low to medium amounts.

Key words: Geographic information system (GIS), spatial variation, soil properties, precision agriculture.