MORPHOLOGICAL AND CHEMICAL PROPERTIES OF SELECTED SLUDGE-AMENDED NIGERIAN SOILS

Abstract

Application of sewage sludge to agricultural lands is one way to address the high demand for a low supply of commercial fertilizers in Nigeria. This study was conducted to investigate the morphological and chemical properties of sludge-amended soils after about 37 years of sludge application. Two soils on a 5-ha sewage farm and a soil at a nearby, unamended site were selected for the study. Soil at all three sites would have been mapped and classified in the same soil series before application of sewage sludge. The unamended soil was a fine-loamy, kaolinitic, isohyperthermic Rhodic Kandiustult. Compared with the unamended soil, the sludge-amended soils had better aggregation in the surface horizon, greater total soil C and N, and higher levels of exchangeable bases. After 37 years of sewage sludge amendment, a higher base saturation percentage in the subsurface horizons of one sludge-amended soil led to its classification as an Alfisol instead of an Ultisol. Base saturation in the subsurface of the other amended soil was very close to that required for Alfisols, but it would still be classified as an Ultisol.