Lime and Manure Application to Low-fertility Tropical Soils Enhances Phosphorus Bioavailability for Increased Agronomic Productivity

Liming and manuring to ameliorate soil acidity and enhance mineralization in acid tropical soils could promote their agronomic productivity.Synthetic lime and poultry-droppings manure’seffects in sandy-loam Ultisols were evaluated on soybean growth, exploring its relationships with soil pH, soil available P and plant P content. Lime was applied at 0, 2.5 and 5 t ha-1 equivalents and manure at 0, 25 and 50 t ha-1 equivalents to 2.5-kg potted soils. Crop growth data were collected during andsoil-plant analysis after sixweeks of growth. Treatment had more pronounced effects on plant height than leafiness, beinggenerallyhighest in lime 2.5 + manure 50 where the plants were about 3 x taller comparedtounamended control. Soybean grew better due to 2.5 than 0 and 5 t ha-1 lime, and to 50 than 0 and 25 t ha-1 manure. Plant heightand leaf area depended on soil pH’s influence on soil available P (R2 = 0.69**) and plant P content (R2= 0.85**), respectively, whileabove-soil biomass on soil pH or plant height (R2 = 0.74**). Moderate liming (2.5 t ha-1) with ample manuring (50 t/ha) could enhance crop early-stage vegetative growthin low-fertility tropical soils, due largely to amelioration of soil acidityto enhance uptake of bioavailable P.