Phosphorus mineralization potentials of some organic amendments applied to degraded tropical Ultisol

Information on phosphorus (P) mineralization pattern of organic amendments is germane for proper P management. This study was to determine phosphorus mineralization potentials of some organic amendments applied to degraded tropical Ultisol. The experiment was a 4×10 factorial set-up fitted in Completely Randomized Design. Treatments were soil amendments (Control, poultry manure, biosolids, and biochar) and period of incubation (0, 10, 20, 30, 40, 50, 60, 70, 80, 90 days after incubation (DAI)). Soil samples were treated with these amendments equivalent to 60 kg P ha-¹ and incubated for a period of 90 days. Soil samples were collected at 10 day interval for determination of available P. Results showed P mineralization varied significantly across the days of incubation and among the soil amendments. In control soil, available P increased gradually from 10.5 to 25.8 mg kg-¹ (0 - 70 DAI), then slightly declined to 24.6 mg kg^-1 at 90 DAI. Poultry manure amended soil showed rapid rise in available P (42.8 to 67.2 mg kg^-1)  from 0 – 60 DAI, then declined to 58.3 mg kg^-1 at 90 DAI whereas in biosolids amended soil, steady increase from 14.2 to 41.9 mg kg^-1 (0 – 80 DAI), stabilizing to 40.5 mg kg^-1 at 90 DAI. In biochar amended soil, there was continuous increase in available P (27.5 – 59.2 mg kg^-1) throughout 90 DAI, indicating ability of the amendment to support long-term P supply. Conclusively, application of the organic amendments 40 - 60 days before planting is germane for optimal P availability.