Phosphorus is an essential element for plant metabolism and growth, but its future supply under elevated levels of atmospheric CO₂ remains uncertain. Here we present measurements of phosphorus concentration from two long-term (15 and 9 years) rice free air carbon dioxide enrichment experiments. Although no changes were observed in the initial year of the experiments, by the end of the experiments soil available phosphorus had declined by more than 20% (26.9% and 21.0% for 15 and 9 years, respectively). We suggest that the reduction can be explained by the production of soil organic phosphorus that is not in a readily plant-available form, as well as by increased removal through crop harvest. Our findings further suggest that increased transfers of plant available phosphorus from biological, biochemical and chemical phosphorus under anthropogenic changes are insufficient to compensate for reductions to plant available phosphorus under long-term exposure to elevated CO₂. We estimate that reductions to rice yields could be particularly acute in low-income countries under future CO₂ scenarios without the input of additional phosphorus fertilizers to compensate, despite the potentially reduced global risk for phosphorus pollution.

_{磷是植物新陈代谢和生长的必需元素，但其未来在大气 CO 2}水平升高的情况下的供应仍然不确定。在这里，我们展示了两个长期（15 年和 9 年）水稻无空气二氧化碳富集实验的磷浓度测量结果。尽管在实验的第一年没有观察到变化，但到实验结束时土壤有效磷下降了 20% 以上（15 年和 9 年分别为 26.9% 和 21.0%）。我们认为，这种减少可以通过土壤有机磷的产生来解释，这种土壤有机磷不是一种容易被植物利用的形式，也可以通过作物收获增加去除来解释。我们的研究结果进一步表明，在人为变化下，植物有效磷从生物、生化和化学磷的转移增加不足以补偿长期暴露于升高的 CO2 下植物有效磷的减少₂ . _{我们估计，在未来的 CO 2}情景下，如果不投入额外的磷肥来补偿，低收入国家的水稻产量下降可能会特别严重，尽管全球磷污染风险可能会降低。