Combined Effect of Cattle Dung and Urea Fertilizer on Organic Carbon, Forms of Nitrogen and Available Phosphorus in Selected Nigerian Soils

Incubation experiment was conducted on four soil types in Nigeria using cattle dung (CD) at the rate of 2.5g/kg soil ( 5 t ha), Urea fertilizer at the rate of 0.1g/kg soil ( 200 kg ha ) and cattle dung (2.5g/kg soil) combined with Urea 0.05g/kg soil (100 kg ha) as treatments. The objective of the experiment was to compare the rate of OC, NH4 – N, NO3 – N and available P release on soils selected from different agro ecological zones of Nigeria. Ten soil samples were collected and bulked from each of the sandy clay, sandy loam, sandy clay loam and loamy sand soils from three different locations within each soil type. The soils were arranged on completely randomized design in laboratory for 60 days. All the treatments reacted differently in each of the soil type in relation to OC, total N, NH4 – N, NO3 – N and available P. In sandy clay and sandy loam soils, all the treatments significantly increased (p < 0.05) OC, total N, NH4 – N, NO3 – N and available P except OC in sandy loam compared with control. In sandy clay loam and loamy sand soils, all the treatments significantly increased (p< 0.05) NH4 – N, NO3 – N and available P. Among all the treatments, CD had the highest OC in all the soil textural classes,, urea had the highest NH4-N and NO3-N while CD + urea had the highest available P (except sandy clay). Cow dung had the highest P in sandy clay. Sand loam and sandy clay loam had highest total N but urea recorded highest value of N in sandy clay while urea+CD mineralized equal amount of total N