Agronomic and socio-economic assessments of the roles of earthworms and termite mounds in paddy fields

Abstract

Bioturbation, the physical disturbance and mixing of soil layers caused by the activity of living organisms, such as earthworms and termites, plays a critical role in shaping soil structure, enhancing nutrient cycling, and regulating ecosystem dynamics. In paddy fields, earthworms form cast-hills and termites build mounds with distinct soil properties compared to the surrounding soil, potentially influencing soil fertility, pest regulation, and resilience to climatic stress. Although the impact of earthworms and termites on plants is well documented, their broader influence on farming practices and rice production at the plot scale remains poorly understood. The objective of this study is to assess the impact of earthworms and termite mounds on Cambodian paddy field agroecosystems. We hypothesized that these organisms improve soil fertility and rice yields, reduce reliance on fertilizers and pesticides, regulate pest pressure, and enhance drought resilience, thereby supporting farm income and sustainability. Through Partial Least Squares Structural Equation Modeling (PLS-SEM), we observed that earthworm abundance was positively associated with soil silt content and soil nitrogen content, double cropping and higher caterpillar (armyworm) occurrence. Termite mound presence correlated with higher pest presence (snails, crabs, brown plant hoppers), higher input use, and farmers' perceived drought risk, but not with soil properties. However, neither earthworms nor termites had direct or indirect effects on rice yield or income. These findings highlight the complex ecological roles of these two soil engineers, while suggesting that their contribution to rice productivity and income remains limited, underscoring further research in food-crop-based agroecosystems.