Fate of phosphorus fertilizer in acidic Cambisol assessed using 33P isotope labeling technique


Author(s): Deejay Maranguit1*,2 and Yakov Kuzyakov2,3

Abstract

Direct 33P labeling approach is a very powerful technique that has high sensitivity in tracing the fate of added phosphorus (P) fertilizers across various P pools. Nonetheless, only a few studies have used this approach. This study traced the fate of applied P fertilizer in acidic P-limited soil using the 33P labeling approach.The incorporation of 33P-labeled KH2PO4 in available P (PAEM), microbial biomass P (Pmic) and Fe/Al-bound P (PNaOH) pools was followed in Cambisol as influenced by C and N sources applied as glucose and ammonium sulfate, respectively.Results showed that not all of the added P fertilizer remains in available pool; instead, it was distributed to poorly-available pools. Fast, almost instantaneous P fixation by the Fe and Al oxides and immobilization by microbial uptake were recorded.Applying glucose boosts microbial growth and demand for P, resulting in increased 33P recovery. High 33P recovery in Pmic (20% of the applied 33P) and in PNaOH (45% of applied 33P) showed the dominance of P immobilization by microorganisms and adsorption by Fe and Al oxides on the fate of P in an acidic soil. Nevertheless, these can contribute to long-term P availability after the turnover of microbial biomass and desorption of fixed P.

Keywords: 33P isotopic labeling; Phosphorus dynamics; Phosphorus availability; Phosphorus fractions; Microbial biomass P; P-limited soil