Poultry Manure and Nitrogen–Phosphorus–Potassium Fertilizer Application and Their Residual Effects on Soil Physical Properties in Two Distinct Ecological Zones of Central Southern Nigeria

Abstract

Poultry manure and nitrogen–phosphorus–potassium (N–P–K) fertilizer application and their residual effects on soil physical properties were investigated with soils drawn from two distinct ecological zones, Agbede (derived savanna) and Obadan (forest), of Edo State of southern Nigeria in 2005 and 2006 rainy seasons. The treatments consisted of three levels of poultry manure (0, 4, and 6 tons/PM/ha) and four levels of NPK 15:15:15 fertilizer (0, 50, 100, and 150 kg NPK ha−1), which were combined factorially, arranged in a randomized complete block design, and replicated three times. Poultry manure, combined application of poultry manure and NPK fertilizer in 2005, and their residual effects in 2006 gave greater degree of saturation and soil moisture content and lower soil bulk density in both locations but were significantly better in the Obadan location in 2006. The lowest bulk densities of 1.16 and 1.15g cm2 were obtained with the application of 6 tons PM ha−1 + 50 kg NPK ha−1 in Obadan soils in 2005 and 2006, respectively. Water-stable aggregate, porosity, void ratio, and air-filled porosity were greater in 2006 due to the residual effects of poultry manure and its combined application with NPK fertilizer than in 2005. In contrast, fertilizer application alone reduced void ratio, porosity, and air-filled porosity of the soils.