Organic phosphorus (P_o) plays an important role in tropical forest nutrition on strongly-weathered soils. However, of its role in Eucalyptus nutrition little is known. For this purpose, soil P forms were determined by NaOH-Na₂EDTA extraction and ³¹P nuclear magnetic resonance spectroscopy (³¹P NMR) at 10 sites of Eucalyptus plantations in Brazil. The objectives were (1) to determine the amounts and forms of soil P_o; (2) to build a structural model of the soil P cycle to provide quantitative estimates of the transformation processes of soil P. Soil P was found to consist of large amounts of Monoesters-P (on average 43.7 mg kg⁻¹) followed by Diesters-P in the form of DNA (on average 4.2 mg kg⁻¹), as well as containing high reserves of P_i species (on average 101.6 mg kg⁻¹ of the ortho-P; 2.7 mg kg⁻¹ of the pyrophosphate). Thestructural model indicated that the P cycle is regulated by clay, soil organic carbon, total P and pH. High total P_o concentrations (on average 48 mg kg⁻¹) reveal a high potential of P supply to Eucalyptus trees, in which Diester-P (DNA) would be the main source P for the available P pool. The close interconnection between ortho-P, pyrophosphate, DNA and Monoester-P compounds provides evidence of a strong influence of soil biological activity on the distribution and accumulation of these P compounds and therefore on the availability of P. Thus, these results are relevant to establish soil fertility management strategies for low-fertilizer input Eucalyptus systems in soils with low fertility.

有机磷（P _o）在强风化土壤上的热带森林营养中起着重要作用。然而，其在桉树营养中的作用鲜为人知。为此，在巴西的10个桉树人工林中，通过NaOH-Na ₂ EDTA萃取和³¹ P核磁共振波谱法（³¹ P NMR）确定了土壤P的形态。目的是（1）确定土壤P _o的数量和形式；（2）建立土壤磷循环的结构模型，以提供对土壤磷转化过程的定量估计。土壤磷被发现由大量的单酯-P组成（平均43.7 mg kg ^-1），然后是DNA形式的Diesters-P（平均4.2 mg kg ^-1），并且含有高储备的P _i物种（邻位P的平均含量为101.6 mg kg ^-1； 2.7 mg kg ^-1的焦磷酸盐）。结构模型表明，磷的循环受粘土，土壤有机碳，总磷和pH的调节。高的总P _o浓度（平均48 mg kg ^-1）显示了向桉树供应P的潜力很大，其中Diester-P（DNA）将成为可用P库的主要P来源。正交之间的紧密互连-P，焦磷酸盐，DNA和单酯-P化合物提供了土壤生物学活性对这些P化合物的分布和积累以及因此对P有效性的强烈影响的证据。因此，这些结果与建立土壤肥力管理策略有关用于低肥力土壤中的低肥料输入桉树系统。