To improve phosphorus (P) fertilization and environmental assessments, a better understanding of release kinetics of solid-phase P to soil solution is needed. In this study, Fe (hydr)oxide-coated filter papers (Fh papers), isotopic exchange kinetics (IEK) and chemical extractions were used to assess the sizes of fast and slowly desorbing P pools in the soils of six long-term Swedish field experiments. The P desorption data from the Fh-paper extraction of soil (20 days of continual P removal) were fitted with the Lookman two-compartment desorption model, which estimates the pools of fast (Q₁) and slowly (Q₂) desorbing P, and their desorption rates k₁ and k₂. The amounts of isotope-exchangeable P (E) were calculated (E_1min to E_{>3 months}) and compared with Q₁ and Q₂. The strongest relationship was found between E_{1 min} and Q₁ (r² = .87, p < .01). There was also an inverse relationship between the IEK parameter n (the rate of exchange) and k₁ (r² = .52, p < .01) and k₂ (r² = .52, p < .01), suggesting that a soil with a high value of n desorbs less P per time unit. The relationships between these results show that they deliver similar information, but both methods are hard to implement in routine analysis. However, Olsen-extractable P was similar in magnitude to Q₁ (P-Olsen = 1.1 × Q₁ + 2.3, r² = .96), n and k₁ were related to P-Olsen/P-CaCl₂, while k₂ was related to P-oxalate/P-Olsen. Therefore, these extractions can be used to estimate the sizes and desorption rates of the different P pools, which could be important for assessments of plant availability and leaching.

中文翻译：

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农业土壤中的磷解吸和同位素交换动力学

为了改进磷 (P) 施肥和环境评估，需要更好地了解固相磷释放到土壤溶液中的动力学。在这项研究中，使用铁（氢）氧化物涂层滤纸（Fh 纸）、同位素交换动力学（IEK）和化学提取物来评估六个长期瑞典田地土壤中快速和缓慢解吸 P 池的大小实验。来自 Fh 纸提取土壤的 P 解吸数据（连续 P 去除 20 天）符合 Lookman 两室解吸模型，该模型估计快速（Q ₁）和慢速（Q ₂）解吸 P 的池，以及它们的解吸率k ₁和k ₂. 计算同位素可交换 P (E) 的量（E _1min至 E _{>3 个月}）并与 Q ₁和 Q ₂进行比较。_{在 E 1 min}和 Q ₁ ( r ²  = .87, p  < .01)之间发现了最强的关系。IEK 参数n（汇率）与k ₁ ( r ²  = .52, p  < .01) 和k ₂ ( r ²  = .52, p < .01)之间也存在反比关系 ，这表明具有高价值的土壤n每单位时间解吸的 P 较少。这些结果之间的关系表明它们提供了相似的信息，但两种方法都难以在常规分析中实施。然而，Olsen 可提取 P 的大小与 Q ₁相似（P-Olsen = 1.1 × Q ₁ + 2.3，r ²  = .96），n和k ₁与 P-Olsen/P-CaCl ₂相关，而k ₂与P-草酸盐/P-Olsen有关。因此，这些提取物可用于估计不同 P 池的大小和解吸率，这对于评估植物可用性和浸出可能很重要。