Phosphorous transformation as influenced by different levels of phosphorous alone and in combination with humic acid

An incubation experiment was carried out in completely randomized design (CRD) at the laboratory of soil and environmental sciences, the university of Agriculture Peshawar, Pakistan to investigate changes in AB-DTPA extractable soil Phosphorous (P) with the addition of Humic acid (HA) and added P levels as single super phosphate (SSP). Two levels of HA including control (H0: control and H1: 500 g ha-1) and four levels of P as single super phosphate (SSP) including control (P0: control, P1: 60 kg ha-1, P2: 90 kg ha-1, and P3: 150 kg hectare) were utilized. Soil treated with different levels of SSP alone or reinforced with HA showed an initial decline in AB-DTPA extractable P in first 14 days and then rapid mineralization up to 56 days of incubation in the laboratory. HA increased mean available P by 44.93, 16.08 and 7.25 % at 0, 60 and 90 kg P205 ha-1. Weekly turnover of P ranged from 0.19 to 0.43 mg P kg-1 soils for soils treated with different levels of SSP alone or reinforced with HA. HA increased weekly turnover by 40 and 8.82 % at 60 and 90 kg P205 ha-1 as SSP respectively. HA applied alone or reinforced with 60 and 90 kg P205 ha-1 increased mean available P, weekly turnover of P as well as mineralization potential.