Multi-location assessment of variability and relationships of phosphorus fixation, fractions, availability and recovery under high P Alfisols

A study was conducted to assess P-fixation, P-fractions and availability of P under selected high P soils under semi-arid Alfisols in Nizamabad of Telangana and Guntur and Kurnool districts of Andhra Pradesh. A survey was carried out for recording occurrence of high-P soils in Varni, Mangalagiri and Velugodu locations of Nizamabad, Guntur and Kurnool, respectively. The survey revealed that high-P soils in these three locations were 98, 71 and 77%, respectively. Three soil samples from each location (categorized into high, very high and extremely high for soil P) were selected and studied under laboratory conditions. The soils were studied for Pfractions, P-fixation and recovery of applied P. Within each location, soils exhibited an increase in the amount of each fraction of P with increasing soil P. An incubation study was undertaken with P³² isotope to understand available and recovery of applied P. Observations were recorded at 3 contact periods viz., 15, 30 and 45 days after incubation (DAI). The soil P decreased with increase in DAI under the 3 soil fertility situations. The percent P derived from fertilizer (PDFF) in different locations increased with increase in P levels in all soils with increase in DAI. Within each soil, PDFF decreased with increase in initial P. The percent recovery of P was higher at Velugodu (52%), followed by Mangalagiri (50%) and Varni (39%) when compared between 25 to 100% recommended P application. The recovery of P increased with increase in P application at all locations. Based on the study, the high P soils could be efficiently managed by assessing the relationships of phosphorus fixation, availability, fertilizer application and recovery under Alfisols.