Effectiveness of Sugar Industry Organic Wastes in Reducing Soil Compatibility in Soils of Three Ethiopian Sugar Estates

Abstract

Incorporation of sugarcane industry by-products into soil can reduce the susceptibility of soils to compaction. However, the significance of incorporated filter cake and filter cake compost at different soil water contents at the time of compaction using proctor test load is not well documented. In this context, study was conducted at three Ethiopian sugar Estates in 2017 to examine the effect of filter cake and filter cake compost incorporation to three soils different in clay content on soil maximum dry density, total porosity at MDD, critical moisture content under laboratory conditions. Sugarcane residues were added to soils at rates of 0, 7.75 g of residues per kg of soils. The results of the study showed that the maximum dry bulk density with no sugarcane residue added was achieved at 15.94% for light, 25% for medium and 28.6% for heavy clay. Filter cake incorporated at the rate of 30 t ha-1 reduced the soil compactibility induced by proctor test load at water content of 0.7 PL for light clay soils, 0.97 PL for medium clay and at water content of 0.98 PL for the heavy clay soils. In all three soil types at 0 t ha-1 and 30 t ha-1 residue application levels, the total porosity attained a minimum value at critical moisture content and critical moisture content for the maximum dry density increased as the clay content increased. Filter cake and filter cake compost reduced the maximum dry density of heavy clay soil by 4 and 27.6%, respectively, as compared to the control. Nevertheless, this residues increased total porosity at critical moisture content, respectively, by 2.44 and 46.9% over the control for heavy clay soils. Therefore, it can be concluded that sugarcane residue was most effective in reducing soil compactibility at moisture content less than PL compared to water content higher than PL. Moreover, filter cake compost was more effective in reducing soil compactibility than filter cake. Finally, the study recommended that the heavy machineries operation during sugarcane seedbed preparation and harvesting; shall be made when soil moisture is below 0.60, 0.9 and 0.91 PL, respectively, for light, medium and heavy clay soils and after treating the soil with either filter cake or filter cake compost tentatively. Nevertheless, in order to give conclusive recommendation further research studies are needed for more soil clay levels for the case of filter cake compost and more rates for both sugarcane residues.