Effect of different phosphorus sources on P-uptake and yield of rice in acidic soil: a study of phosphorus availability dynamics

Phosphorus (P) limitation in acidic soils is well known and P-use and -recovery efficiency (PUE and PRE) is quite low. Rhizosphere-based P management has been considered as a means of enhancing PUE in acidic rice soils, but no clear dynamic study on this context. Rice was grown in pots using different P-sources [rock-phosphate (RP), single-super-phosphate (SSP), compost, P solubilizing bacteria (PSB), PSB + RP, PSB + compost, and compost + PSB + RP] in acidic Inceptisols (pH 4.31). Additionally, a micro-plot field experiment validated the results, using control, SSP, RP, PSB, and PSB + RP. Available-P (AvlP) and pH were analyzed every 10-days, while acid-phosphomonoesterases activity (PHA) and P-uptake in every 30-days until harvest. AvlP was peaked at 20 days after transplanting (DAT) and decreased until harvest. Compost + PSB + RP maintained significantly higher AvlP, soil pH and PHA, while root volume was highest in SSP throughout the growing period, and Soil pH showed an asymptotic trend. The P-content and uptake in biomass showed the highest peak at 60DAT and gradually declined until harvest. The effects of SSP and compost + PSB + RP on grain yield, chlorophyll concentration index (CCI), grain P content and uptake were comparable, but PUE and PRE were higher in compost + PSB + RP. Similar result was also observed in micro-plot field experiment, wherein grain yield and P uptake were comparable in SSP broadcast and PSB + RP. The study clearly shows that the combined application of PSB with RP, compost, or both in a 50% reduced amount can maintain higher AvlP in rice in acidic soil compared to full dose SSP while achieving a comparable yield.