Response of Soil-dwelling Insects and Weed Communities to Fertilizer Management in Cassava Production: A Site Comparison Study in Agusan Del Sur, Philippines

Aims: Intensification of cassava production through improved fertilizer management requires understanding its impacts on agricultural biodiversity. Study Design: A field experiment using a split-plot design with three replications. Place and Duration of the Study: The study was conducted at two sites (Research Station and farmer's field) from April 2021 to March 2022. Methodology: The study compared eleven fertilizer treatments across two cassava varieties (Lakan 1 and Golden Yellow). Soil-inhabiting insects and weed communities were assessed across all treatments. Results: Soil-inhabiting insects showed significantly higher populations in unfertilized control plots compared to fertilized treatments, with predatory ground beetles (Carabidae) dominating both sites. Shannon's diversity indices (1.58-1.62) indicated moderate insect diversity across sites, suggesting simplified but functional communities. Weed assessments revealed distinct community structures between sites, dominated by perennial grasses from the Poaceae family. While fertilizer treatments significantly influenced soil insect abundance, weed community composition was more strongly affected by site-specific conditions, as demonstrated through cluster analysis. Conclusion: The study demonstrates that agricultural intensification through fertilizer application may impact beneficial soil fauna while having limited effect on weed community structure. These findings suggest the need for integrated, site-specific management approaches that balance nutrient application with biodiversity conservation in cassava production systems.