This study was set up to identify the role of the phosphorus (P) desorption rate in P diffusion and in P bioavailability in soil. The P desorption kinetics were measured with a zero‐sink method in soil suspensions (0–77 days) for a set of soils that either had or had not been mined for P in a glasshouse study. The desorption kinetics was fitted by a serial two‐pool model, discriminating a fast desorbing P pool (Q₁) with desorption half‐lives of 3–8 days, and a slowly desorbing P pool (Q₂), which replenishes the fast P pool with 100‐fold larger half‐lives than the fast pool. Phosphate desorption was smaller and slower after soil P mining compared to that in the original soil samples and mining reduced the Q₁/Q₂ ratio. This kinetic model was embedded in a 1D planar diffusion model predicting that the diffusive flux of P to a zero sink in 5 days varies by a factor of 1.4 among the observed Q₁ desorption rate constants, keeping other parameters constant, and that the reduced Q₁/Q₂ ratio upon P mining sharply reduces the diffusible P in soil. The P uptake model of Barber‐Cushman was extended with P desorption kinetics and was successfully calibrated to the P uptake data of the glasshouse P mining study. The model correctly predicted that reduced nitrogen (N) fertilization enhances the soil P‐use efficiency because of lower critical P demand rates at slower growth. Finally, that new model predicted that maize requires >3‐fold more available P in soil than wheat because of a higher P demand rate per unit root area of maize than that of wheat. This confirms a similar factor difference in critical soil P concentrations observed in P‐response trials in Belgium between 1973 and 2018. This study shows that the P desorption rate limits P bioavailability for fast growing plants with a small effective root area, especially under negative soil P balances that slow down the desorption rate of P in soil.

中文翻译：

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土壤中磷酸盐的解吸速率限制了作物对磷的生物利用度

进行这项研究的目的是确定磷解吸速率在土壤中磷扩散和磷生物利用度中的作用。在温室研究中，采用零沉法在土壤悬浮液（0-77天）中对一组已开采或未开采过P的土壤中P的解吸动力学进行了测量。解吸动力学由串行两池模型拟合，区分了具有3–8天解吸半衰期的快速解吸P池（Q ₁）和补充了快速P的缓慢解吸P池（Q ₂）。池的半衰期比快速池大100倍。与原始土壤样品相比，土壤磷开采后的磷酸盐解吸更小且更慢，采矿降低了Q ₁ / Q ₂比。将该动力学模型嵌入到一维平面扩散模型中，该模型预测在观察到的Q ₁解吸速率常数中，P在5天内向零沉的扩散通量变化1.4倍，保持其他参数不变，并且降低的Q ₁ / Q ₂磷开采时的磷比率可显着降低土壤中可扩散的磷。Barber-Cushman的P吸收模型扩展了P的解吸动力学，并成功地根据温室P采矿研究的P吸收数据进行了校准。该模型正确地预测，减少氮（N）的施肥会提高土壤磷的利用效率，因为在生长缓慢的情况下较低的临界磷需求率。最后，该新模型预测，玉米对土壤的有效磷需求要比小麦高三倍以上，因为玉米的单位根面积对磷的需求率要高于小麦。这证实了1973年至2018年在比利时的磷响应试验中观察到的关键土壤磷浓度存在相似的因子差异。这项研究表明，磷的解吸速率限制了有效根系面积小的快速生长植物的磷生物利用度，