The plant uptake of legacy phosphorus (P) from over-fertilised agricultural soils could offer a solution to decrease dependency on finite mineral P resources. This study evaluated the long-term availability of legacy P in soils with an accelerated biological mining assay, thereby testing to what extent this availability is affected by soil organic carbon (SOC). A 15-month-long pot trial was set-up, in which 25 soils with 1.2–24% SOC were mined for P by continuous cropping and harvesting of ryegrass (Lolium perenne) in a plant growth cabinet. The cumulative uptake of P was, on average, 19% of the P associated with poorly crystalline iron (Fe) and aluminium (Al) (oxy)hydroxides (oxalate-extractable P; P_ox). On average, half of this P could be taken up at rates fast enough to maintain crop production at > 90% of its potential. This P taken up before a 10% reduction in yield occurred, termed the critical cumulative P uptake (CCP), strikingly matched with the isotopically exchangeable P or “E value” of a soil (median CCP/E_24h = 0.81), whereas it was markedly underestimated by Olsen P (median CCP/P_Olsen = 1.51). The fractions of plant-available P_ox increased at increasing ratios of either P or SOC to the sum of Fe_ox and Al_ox, suggesting that enhanced SOC contents reduce ageing of P by preventing its diffusion into micropores. That effect of SOC on P availability was more pronounced in soils with a low initial P saturation status. The comparison of the results from biological mining with available soil P pools determined in a (sterile) P desorption experiment could not confirm a significant contribution of organic P to plant P supply. Based on the set of soils in our study, our findings suggest that legacy P in well-fertilised agricultural soils could act as a sufficient P source for plants for several years to decades, and that this long-term availability is positively affected by SOC as long as the soil is not saturated with P.

植物从过度施肥的农业土壤中吸收遗留磷 (P) 可以提供一种解决方案，以减少对有限矿物磷资源的依赖。本研究通过加速生物开采分析评估了土壤中遗留磷的长期可用性，从而测试了这种可用性在多大程度上受土壤有机碳 (SOC) 的影响。建立了一个为期 15 个月的盆栽试验，其中通过在植物生长柜中连续种植和收获黑麦草 ( Lolium perenne ) ，在 25 个 SOC 为 1.2-24% 的土壤中开采 P。P 的累积吸收平均为与结晶性差的铁 (Fe) 和铝 (Al) (氧) 氢氧化物（草酸盐可萃取 P；P _{ox ）相关的 P 的 19%}）。平均而言，该磷的一半可以以足够快的速度被吸收，以将作物产量维持在其潜力的 90% 以上。该 P 在产量减少 10% 之前被吸收，称为临界累积 P 吸收 (CCP)，与土壤的同位素可交换 P 或“E 值”惊人地匹配（中值 CCP/E _24h  = 0.81），而它被 Olsen P 明显低估（中值 CCP/P _Olsen  = 1.51）。植物可利用的 P _ox的比例随着 P 或 SOC 与 Fe _ox和 Al _{ox总和的比率的增加而增加}，表明增加的 SOC 含量通过阻止 P 扩散到微孔中来减少 P 的老化。SOC 对 P 有效性的影响在初始 P 饱和状态较低的土壤中更为明显。将生物开采的结果与（无菌）磷解吸实验中确定的可用土壤磷库进行比较，不能证实有机磷对植物磷供应的显着贡献。基于我们研究中的一组土壤，我们的研究结果表明，施肥良好的农业土壤中的遗留磷可以作为植物在几年到几十年内的充足磷源，并且这种长期可用性受到 SOC 的积极影响，因为只要土壤没有被磷饱和。