Laboratory and greenhouse experiments were conducted on a lateritic sandy loam soil mixed hyperthermic, Ultic Haplustalf to determine the influence of several (natural and synthetic) soil conditioners at different concentrations on soil aggregation, porosity, soil water retention, saturated hydraulic conductivity, and crop growth. The conditioners were applied in solution at the rates of 0.05, 0.10, and 0.20% by spraying the solution, followed by mixing with the soil to facilitate aggregation. Only polyvinyl alcohol with borax and guar gum, guar gum + borax, and guar gum alone significantly increased the water-stable aggregates (2-4 mm diameter), reduced macropores (>30 ?m), increased water retention capacity, and decreased hydraulic conductivity of the soil. The effect of increased concentration was not similar for all conditioners. In general, increasing the concentration further improved the soil physical properties. Conditioners significantly increased total dry matter of the plants. The maximum increase was obtained with guar gum + borax-treated soil, and the minimum under polyvinyl alcohol with guar gum and borax and lignosulphonate treatments. The natural conditioner guar gum with borax (1 ppm) and polyvinyl alcohol were superior to synthetic or natural conditioners alone.