Assessment of Soil Physical Degradation Under Intensive Cassava Cultivation in Delta State, South South Nigeria

This study assesses physical soil degradation indicators under intensively managed cassava cultivation compared to fallow land in Delta State, located in Nigeria's South South geopolitical zone. Cassava is the dominant food and industrial crop in Delta State, and its intensive cultivation on continuous short-rotation cycles without adequate organic matter replenishment or conservation tillage has raised concerns about progressive physical soil quality decline. Using a comparative field design, soil physical properties were assessed on 20 intensively cultivated cassava plots and 10 corresponding fallow plots across Oshimili North, Ethiope East, and Okpe local government areas. Measurements included bulk density by core sampling, penetration resistance by pocket penetrometer, aggregate stability by wet sieving, saturated hydraulic conductivity by the falling-head method, and visual assessment of surface sealing and compaction. Findings revealed that cassava plots had bulk density values 18 percent higher than fallow plots, penetration resistance 35 percent higher, and water stable aggregate content 42 percent lower. Saturated hydraulic conductivity was reduced by 62 percent in cassava plots relative to fallow, indicating significant structural deterioration affecting drainage and root aeration. Long-rotation plots (greater than two years fallow) showed intermediate values, demonstrating partial soil recovery under rest. The study recommends minimum tillage, retention of cassava stem and peel organic matter on the field, and regular fallow cycles of at least 18 months to restore physical soil quality in Delta State cassava systems. Keywords: soil physical degradation, cassava cultivation, Delta State, bulk density, soil structure.