Impact of topsoil mining for unfired mudbricks on soil quality in eastern KwaZulu-Natal, South Africa

Abstract

Topsoil mining associated with informal mud brick making is common in rural villages of South Africa. The impact of topsoil mining on soil quality, however has not been investigated. This study therefore assessed the impact of topsoil mining associated with unfired mud bricks on selected soil quality indicators in two villages of KwaZulu-Natal, South Africa. First, local miners were interviewed to ascertain information related to topsoil mining, brickfield site identification and soil suitability for mud bricks. Two brickfields per village mined for ≤5 and > 20 years, respectively were used in this study. Experiment consisted of three treatments, that is, unmined, mined and recovering lands replicated three times. Nine soil samples were collected (0–10 cm) from each site (three composite samples per treatment) with corresponding bulk density samples taken at 0–5 cm using core rings. The average topsoil mining depth was 30 cm. Interviews revealed that isidaka (poorly drained sandy clay) and isibomvu (red soil) are preferred over ubumba (clayey) soils. Topsoil mining increased silt fraction across all studied brickfields with an average of 45.2% in mined compared with 30.6% in unmined treatments. The response of clay fractions was variable across villages and mining time. Mining significantly decreased mean weight diameter, exchangeable bases, organic carbon, and nitrogen content and stocks and porosity while it increased bulk density. Results show that topsoil mining for mud brick making results in poor soil physical quality, nutrient availability and carbon storage with implications for land degradation in mud brickfields.