Phosphorus (P) can leach from topsoil in inorganic and organic forms. While some evidence has shown inorganic P (orthophosphate) can leach to depth in some soils, less is known of dissolved organic P (DOP). This is not helped by a paucity DOP data for groundwater. We hypothesized that DOP species would leach in greater amounts to depth and at a faster rate through aquifer gravels than orthophosphate. We applied superphosphate with or without dung to a low P-sorption soil under pasture and irrigation. Between 0.7 (control) and 2.4 (dung +superphosphate) kg P ha⁻¹ was leached through 30 cm with a mean ratio of DRP to DOP of 1.5. At 50 cm, 0.7 and 1.3 kg P ha⁻¹ was leached with the DRP to DOP ratio decreasing to 1.1 due to greater DOP leaching (or DRP sorption). There was little difference in DRP losses measured at 50 and 150 cm depth. All DOP compounds except the monoester – inositol hexakisphosphate were leached at a faster rate than orthophosphate through aquifer gravels. These data suggest that where low P-sorption soils overlay similarly low P-sorption aquifers, DOP may reach groundwater at a faster rate than orthophosphate. Furthermore, as many DOP species are bioavailable to periphyton, our data suggest that DOP should be included in the assessment of the risk of P contamination of groundwater where connection to baseflow could be a long-term stimulant of periphyton growth.

磷（P）可以无机和有机形式从表土中浸出。尽管一些证据表明无机磷（正磷酸盐）可以在某些土壤中浸出至深度，但对溶解有机磷（DOP）的了解却很少。缺乏地下水的DOP数据无济于事。我们假设DOP物种通过含水层碎石比正磷酸盐会更大量地浸入深度并以更快的速率浸出。在牧场和灌溉条件下，我们将过磷酸钙和有或没有粪便的土壤施用到低磷吸附的土壤上。在0.7（对照）至2.4（粪+过磷酸钙）kg P ha ^-1之间浸出30 cm，DRP与DOP的平均比为1.5。在50厘米，0.7和1.3千克P ha ^-1由于更大的DOP浸出（或DRP吸附），DRP与DOP的比值降低到1.1，从而进行了浸出。在50和150 cm深度处测得的DRP损失几乎没有差异。除单酯（肌醇六磷酸酯）外，所有DOP化合物的浸出速率均比正磷酸盐通过含水层砾石的浸出速率快。这些数据表明，在低磷吸收土壤覆盖类似的低磷吸收含水层的情况下，DOP可能以比正磷酸盐更快的速度到达地下水。此外，由于许多DOP物种可被附生植物生物利用，因此我们的数据表明应将DOP纳入地下水P污染风险的评估中，因为与底流的连接可能是长期促进附生植物生长的因素。