Identifying the effects of soil properties on the transformations of phosphorus (P) in highly concentrated fertiliser bands is a critical component in improving P fertiliser use efficiency, but little is known regarding the kinetics of P transformation, including over longer periods of time that are relevant to multiple cropping seasons. In the present study, we utilised a 12-month soil-fertiliser incubation experiment to simulate deep-placed banded P fertilisers, investigating three contrasting soils from Australia, three P sources, and the co-application of potassium (K). Overall, concentrations of soil solution P in the fertosphere decreased substantially over time regardless of soil type and P form. In the Ultisol and Vertisol, this progressive decrease was due to the precipitation of aluminium-phosphates (and, to a lesser extent, magnesium-phosphates) as well as ongoing sorption reactions, whilst in the alkaline Alfisol this progressive decrease was due to precipitation of calcium-phosphates. Despite P precipitation and sorption reactions, concentrations of potentially-plant available P measured by isotopically exchangeable P within 24 h (Ee24h) remained relatively constant between 1 and 12 months for the Ultisol and Vertisol, with this indicating that the ongoing sorption reactions of P in these fertospheres of non-calcareous soils may not necessarily decrease plant availability over time. We also found that co-application of K resulted in further reduction in P availability in all three soils and was mediated by K displacement of other exchangeable cations, thereby increasing precipitation reactions with dominant minerals. To improve P use efficiency in semi-arid cropping environments, optimising P form as a function of soil type is critical, especially for systems that are reliant on subsoil moisture and where highly concentrated fertiliser bands are applied infrequently to supply P over multiple growing seasons.

中文翻译：

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12 个月内三种土壤肥沃圈中磷的有效性和形态


确定土壤特性对高浓度肥料带中磷 (P) 转化的影响是提高磷肥利用率的关键组成部分，但人们对磷转化动力学知之甚少，包括相关的较长时间段内的磷转化动力学。到多个种植季节。在本研究中，我们利用为期 12 个月的土壤肥料培育实验来模拟深埋带状磷肥，研究了来自澳大利亚的三种对比土壤、三种磷源以及钾 (K) 的共同施用。总体而言，无论土壤类型和磷的形式如何，肥沃层中土壤溶液磷的浓度随着时间的推移而大幅下降。在 Ultisol 和 Vertisol 中，这种逐渐减少是由于磷酸铝（以及在较小程度上磷酸镁）的沉淀以及正在进行的吸附反应，而在碱性 Alfisol 中，这种逐渐减少是由于磷酸钙。尽管存在磷沉淀和吸附反应，但对于 Ultisol 和 Vertisol，通过同位素可交换磷在 24 小时 (Ee24h) 内测量的潜在植物可用磷浓度在 1 至 12 个月之间保持相对恒定，这表明磷的持续吸附反应随着时间的推移，这些非钙质土壤的肥沃圈不一定会减少植物的可用性。我们还发现，钾的共同施用导致所有三种土壤中磷的有效性进一步降低，并且是通过其他可交换阳离子的钾置换来介导的，从而增加了与主要矿物质的沉淀反应。 为了提高半干旱种植环境中的磷利用效率，优化磷形态作为土壤类型的函数至关重要，特别是对于依赖底土湿度以及不经常施用高浓度肥料带以在多个生长季节供应磷的系统。