Browsing by Author "Steyl, An-Mari"

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    Earthworms as bioindicators of soil health in a conservation agriculture setting in the Western Cape
    (Stellenbosch : Stellenbosch University, 2023-03) Steyl, An-Mari; Roets, Francois; Strauss, Johann; Nxele, Thembeka; Stellenbosch University. Faculty of Agrisciences. Dept. of Conservation Ecology and Entomology.
    ENGLISH ABSTRACT: Adopting conservation agriculture (CA) principles aims to increase crop production while improving overall soil health. One benefit of adopting these principles is increased biological activity, such as earthworms. Earthworms are essential soil ecosystem engineers and sensitive to management practices, making them suitable as potential soil health indicators. Since conservation agriculture could promote the numbers and activity of earthworms, they can most likely be used as soil health indicators in these systems. However, this has received very little attention in the Mediterranean climatic region of the Western Cape province. This study assessed whether conservation agricultural practices increase earthworm populations and whether earthworms have the potential to be used as indicators of soil health in these systems. The study was based on two experimental farms in the Western Cape province, each with a mixture of different CA crop rotations, varying levels of legume incorporation, and two conventional tillage sites used as controls. Earthworm samples were collected using three different sampling techniques: hand-sorting, mustard extraction and a combination of the two methods during four sampling stages based on crop growing season. The influence of the sampling method, sampling stage and farming system on earthworm abundance and generic richness was tested. Earthworm abundance and generic richness were also correlated against different soil variables to investigate whether earthworms can be indicators of soil health parameters. The hand-sorting method proved sufficient for obtaining a good representation of earthworm fauna in these systems. CA practices, even those with increased utilization of legume crops, did not necessarily benefit earthworm populations. However, a strong link between soil moisture, earthworm abundance, and generic richness appears to be the most crucial factor driving earthworm numbers in this dry region. Furthermore, earthworm abundance only correlated with a few soil variables, indicating that earthworms could potentially not be useful as indicators of soil health in this region. The exception was a strong correlation between earthworm abundance and soil organic carbon content, indicating that earthworms could be used to indicate this agriculturally important soil variable. Based on this study's results, practices that conserve water and increase carbon content in the soil will likely increase earthworm populations in this region and improve the services they provide.