In a laboratory investigation, mineralization of added plant and soil organic P was studied in loamy sand and sandy loam soils (Typic Ustochrepts) incubated with Sesbania aculeata (dhaincha) for periods ranging from 10 to 100 days at field capacity and submergence. Added plant P mineralized at a faster rate than soil organic P. Higher mineralization of added plant and soil organic P under submerged conditions as compared with field capacity was noticed. A hysteresis was observed between the magnitude of the decrease in organic P and that of the increase in inorganic P content in NaHCO3 extraction of soils amended with Sesbania for different periods. The effect was more pronounced under field capacity than under submergence. The study suggests that amount of P released from the added plant residue on decomposition should be considered for P fertilizer scheduling of various crops.
P mineralization, Sesbania aculeata, water regimes, soil P extractant
