AgResearch, Lincoln Science Centre, Private Bag 4749, Christchurch 8140, New Zealand; Faculty of Agriculture and Life Sciences, P O Box 84, Lincoln University, Lincoln 7647, Christchurch, New Zealand.
AgResearch, Invermay Agricultural Centre, Private Bag 50034, Mosgiel 9053, New Zealand.
Sci Total Environ. 2021 Feb 10;755(Pt 1):142392. doi: 10.1016/j.scitotenv.2020.142392. Epub 2020 Sep 18.
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 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 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）可以以无机和有机形式从表土中淋滤出来。虽然有一些证据表明，某些土壤中的无机磷（正磷酸盐）可以淋滤到一定深度，但对溶解有机磷（DOP）的了解较少。地下水中 DOP 数据的缺乏对此没有帮助。我们假设 DOP 会以更大的量和更快的速度通过含水层砾石淋滤到深处，而不是正磷酸盐。我们在低磷吸附土壤上施加了过磷酸钙和/或粪肥，这些土壤处于放牧和灌溉条件下。在 30 厘米的深度范围内，有 0.7（对照）至 2.4（粪肥+过磷酸钙）kg P ha 通过，其中 DRP 与 DOP 的平均比例为 1.5。在 50 厘米处，有 0.7 和 1.3 kg P ha 通过，由于 DOP 淋滤（或 DRP 吸附）增加，DRP 与 DOP 的比例降低至 1.1。在 50 和 150 厘米深度处测量的 DRP 损失几乎没有差异。除了单酯-肌醇六磷酸外，所有 DOP 化合物的淋滤速度都快于正磷酸盐通过含水层砾石。这些数据表明，在低磷吸附土壤覆盖类似低磷吸附含水层的情况下，DOP 可能比正磷酸盐更快地到达地下水。此外，由于许多 DOP 物种对周丛生物是可用的，我们的数据表明，在连接到基流可能是周丛生物生长的长期刺激的情况下，应该将 DOP 纳入对地下水磷污染风险的评估中。
