Soil physical properties of selected soil series in relation to compaction and erosion on farmers’ fields at Abeokuta, southwestern Nigeria

Abstract

This study evaluated physical properties of selected soil series and their implications on the soil compaction and erosion in Abeokuta, southwestern Nigeria. Daily rainfall data (1999–2007) were collected to estimate the rainfall erosivity. Seven soil series (Iwo, Iseyin, Ekiti, Jago, Okemesi, Apomu, and Egbeda) were sampled from 0–15, 15–30, and 30–50 cm depths for particle size distribution, organic carbon, pH, upper plastic limit, and compactibility (Proctor test). Microtopographical changes along and across toposequences of two farmers’ fields cleared mechanically and manually, respectively, were monitored using the erosion pin method. Mean annual erosivity (EI30) was high (7646 MJ mm ha⁻¹ hr⁻¹). Particle size, organic carbon, and pH were similar (p ≥ 0.05), while upper plastic moisture was ≤ 2% among different soil series. Soil-moisture density curves indicated a maximum bulk density of 1.77–1.99 g cm⁻³ for a moisture range of 7.6–14%; while the soils were prone to compaction at low moisture content. Microtopographic changes were found between –2 and 0 cm and –8 and –2 cm on mechanically and manually cleared farmland, respectively. Spatial dependence showed that the soil erosion could be predicted within 5–8 m distance. To avoid erosion and compaction, soil water content should be less than 7.6% before the introduction of mechanical tillage.

Keywords:

• microtopographic change
• soil compaction
• rainfall erosivity
• tillage
• spatial dependence

Acknowledgments

We are grateful for useful comments and suggestions for the improvement made by the editor and the reviewers.