Effects of Landscape Slope Position, Urban Refuse Compost and Sewage Sludge on Soil Properties and Cassava Yield in South Eastern Nigeria

Understanding the effects of landscape slope position and organic waste residues on soil properties and cassava yield is a critical component of site-specific management. A field study was conducted in an Ultisol at Nsukka, southeastern Nigeria to investigate the effects of landscape slope positions and two organic waste residues (urban refuse compost and sewage sludge) on soil properties and cassava yield. The treatment consisted of two landscape slope positions, two organic waste residues, and a control; arranged in a split – plot design in RCBD. The two slope positions - mid slope (26%) and toe slope (5%) occupied the main–plot, while organic residues at the rate of 50% inorganic nitrogen fertilizer requirement of cassava and a control were the sub-plot treatment. The result obtained from this study showed that slope position significantly (p<0.05) influenced the soil properties after harvest. The toe-slope soil was significantly (p<0.05) higher in dry bulk density, water holding capacity, field capacity moisture content and more resistant to mound dispersion by rain drops. The mid-slope soil was significantly (p<0.05) higher in percent water stable aggregates. There was significant difference (p<0.05) between the non-amended plots and the organic wastes amended plots in respect of aggregate stability as measured by percent water stable aggregate (% WSA) index. Post-harvest soil analysis revealed that plots amended with urban refuse compost (UR) and sewage sludge (SS) did not differ significantly in their pH, total porosity, bulk density, water holding capacity, field capacity moisture content, saturated hydraulic conductivity and mound dispersion as measured by length of exposed nail. Weed infestation, fresh shoot and root yield were significantly (p>0.05) higher at the toe slope position. However, percent survival was significantly (p>0.05) higher at mid slope position. Significant interactions of the slope positions and organic residues were observed in bulk density, total porosity and fresh root yield. The highest fresh cassava root yield of 11.63 tha-1 of the study was obtained in plots amended with urban refuse compost under the toe slope position. Urban refuse compost had the least fresh root yield per hectare (1.32 tha-1) when applied in midslope landscape position but highest (11.63 tha-1) when applied in toe-slope landscape position.