Changes in the Properties of a Tropical Ultisol in Response to Short-Term Effects of Fertilizer Management and Continuous Maize Cropping.

The study investigated the short term effects of fertilizer management on the physical and chemical properties of a sandy loam Ultisol under continuous maize cropping.  Soil properties were tested on the maize plot with after a five-year continuous cropping with organomineral and inorganic fertilizer regimes at the Teaching and Research Farm, Obafemi Awolowo University, Ile- Ife, Nigeria. The treatments consisted of mineral fertilizers applied as 400 kg NPK/ha as NPK 15:15:15, 1300 kg Urea/ha and 680 kg SSP/ha and composted organomineral fertilizer applied as 1700 kg/ha. The field was laid out in a Randomized Complete Block Design. The organomineral fertilizer significantly (p < 0.05) improved the soil porosity and saturated hydraulic conductivity at 0-15 cm and 15-30 cm soil depths. Combined application of organomineral fertilizer with NPK (850 kg/ha of organomineral fertilizer and 200 kg/ha NPK) significantly (p < 0.05) increased soil micro-aggregate stability. However, combined application of the organomineral fertilizer and urea significantly improved the soil nitrogen content at 0-15 cm depth. The carbon contents of soil macro-aggregates greater 250 µm was higher in soils that received organomineral fertilizers which also sequester the highest quantity of organic carbon.