Assessment of spatial variability and mapping of soil properties for sustainable agricultural production using geographic information system techniques (GIS)

Abstract

Mapping of soil properties is an important operation as it plays an important role in the knowledge about soil properties and how it can be used sustainably. The study was carried out in a local government area in Oyo state in order to map out some soil characteristics and assess their variability within the area. Soil sampling was carried out in three different locations in the local government area using the cluster sampling technique. Ten samples were collected in each location within a 10 by 10 km area, soil was sampled at two depths (0–20 and 20–40 cm) respectively. The soil samples were air-dried, crushed and passed through a 2 mm sieve before analyzing it for Nitrogen, phosphorus, Potassium, Organic carbon, pH and exchangeable bases in the laboratory while the SAR, ESP% and cation exchange capacity (CEC) were calculated. After the normalization of data classical statistics was used to describe the soil properties and geo-statistical analysis was used to illustrate the spatial variability of the soil properties by using kriging interpolation techniques in a GIS environment. Results showed that the soil properties with high variability in terms of coefficient of variation are available phosphorus and potassium (C.V = >35%), nitrogen, CEC, OC, SAR and ESP were all moderately variable (C.V = 34–15%) while pH had low variability (C.V = <15%). These variations in chemical properties are mostly related to the different soil management practices carried out in the study area and the parent material on which the soil is formed.