Effects of soil management practices on soil fauna feeding activity in an Indonesian oil palm plantation

Optimizing the use of available soil management practices in oil palm plantations is crucial to enhance long-term soil fertility and productivity. However, this needs a thorough understanding of the functional responses of soil biota to these management practices. To address this knowledge gap, we used the bait lamina method to investigate the effects of different soil management practices on soil fauna feeding activity, and whether feeding activity was associated with management-mediated changes in soil chemical properties, in a 15-year-old oil palm plantation. We examined the four management zones: (1) empty fruit bunch (EFB) application along the sides of harvesting paths; (2) chemical fertilization within palm circles; (3) understory vegetation with pruned fronds in inter-row areas; (4) no input in the cleared part of the harvesting paths. Our results showed significantly higher soil fauna feeding activity under the EFB application compared to other management practices, and this was associated with improved soil chemical properties and soil moisture conditions. Principal component analysis on soil properties indicated that 71.2% of variance was explained by the first two principal components (PCs). Soil pH, base saturation and soil moisture contributed positively to PC1, while exchangeable aluminum and hydrogen contributed negatively to PC1. The results demonstrate that different soil management practices at the tree-scale have the ability to create spatial complexity in soil fauna feeding activity and soil chemical properties. This suggests that the practice of EFB application plays an important role in enhancing soil ecosystem functioning in oil palm plantations, which may ultimately contribute to sustainable palm oil production.