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Behavior of phosphorus(P)in flooded rice soil is controlled by iron(Fe)redox cycling in root-zone.In this study,we applied a novel approach—the diffusive gradients in thin films(DGT)technique—for investigating the in-situ distribution of labile phosphorus(P)and Fe in close proximity to Asian rice (Oryza sativa L.)roots at submillimeter to millimeter spatial resolutions during the seedling and booting stages.We conducted a seven-year field experiment under rice-wheat rotation with different P fertilizer treatments.The results showed a significant and strong positive relationship of the average DGT-labile P concentration with soil Olsen P(R2 = 0.77,P ＜ 0.01)and with rice total P concentration(R2 = 0.62,P ＜ 0.05).Furthermore,results on one-and two-dimensional changes of DGT-labile P indicated that fertilization only in the wheat season produced sufficient amounts of labile P in the flooded paddy soils,similar to when fertilizer was applied only in the rice season;dissolved P concentrations,however,were lower.A co-occurrence and significant positive correlation(P ＜ 0.01)between DGT-labile P and Fe indicated Fe-coupled mobilization of P in flooded paddy soils.These results collectively indicated that the DGT technique provided information on in-situ distribution of labile P and its variability in close proximity to rice roots.This suggests that the DGT technique can improve our understanding of in-situ and high-resolution labile P processes in paddy soils and can provide useful information for optimizing P fertilization.