Identification and quantitation of P compounds and its transformation products in a dual P band using X-ray absorption near edge spectroscopy (XANES)

本研究的长期目标是显著提高作物对肥料磷的吸收效率。在短期内，我们的目标是i）使用X射线吸收近边结构（XANES）光谱法鉴定和量化在磷肥的双谱带中形成的磷化合物和硫酸盐; ii）使用XANES及时跟踪这些初始磷化合物的转化; iii）确定将增加磷溶解度并从而增加植物的磷可用性的那些盐组合。高pH土壤中磷肥肥效低的主要原因是土壤-磷肥反应区中磷的迁移速度减慢。这是由于施入的磷与土壤中交换性Ca ~（2+）、Mg ~（2+）迅速反应而进入土壤溶液的结果。已经采取的纠正这一问题的措施包括通过将非磷酸盐与肥料P共同施用来改变土壤-磷肥反应区的化学环境。在最近完成的一项研究中，我们证明了铵的硫酸盐或碳酸盐与磷酸二氢铵或磷酸二氢钾的应用增加了磷的溶解度和化学扩散（Akinremi等人，2006年）。这种增强归因于硫酸盐或碳酸盐和P之间的阴离子竞争置换的可交换或溶解的钙。我们假设，CaSO 4的形成减少了P的沉淀，从而增加了溶液P。然而，沉淀的P的化学形式是未知的，也没有直接证据表明土壤中存在CaSO 4。这项研究将展示“最先进的”光谱技术的应用，以寻找实际的解决方案低磷肥利用率。我们能够识别和量化在双波段中形成的磷矿物质，这将有助于我们找到正确的配方，以提高作物对磷的肥料利用率。磷肥使用效率的提高将通过降低投入成本和减少土壤残留磷为加拿大农民提供经济和环境效益。

The long-term objective of this study is to significantly increase the efficiency of fertilizer phosphorus uptake by the crop. In the short term, our objectives are i) to identify and quantify the phosphorus compounds and sulphate salts that are formed in dual bands of P fertilizer using X-ray absorption near edge structure (XANES) spectroscopy; ii) to follow the transformation of these initial P compounds in time using XANES and iii) to determine those salt combinations that will increase P solubility and thereby P availability to plants. Low phosphate fertilizer efficiency in high pH soils is primarily due to the slowing down of P movement in the soil-P fertilizer reaction zone. This is caused by rapid reaction of the applied P with soil components such as exchangeable Ca2+ and Mg2+ displaced into soil solution. Measures that have been taken to rectify this problem include the modification of the chemical environment of soil-P fertilizer reaction zone through the co-application of non-phosphatic salts with fertilizer P. In a recently completed study, we demonstrated that the application of sulphate or carbonate salts of ammonium with either monoammonium phosphate or monopotassium phosphate increased the solubility and chemical diffusion of phosphorus (Akinremi et al. 2006). This enhancement was attributed to anionic competition between sulphate or carbonate and P for the displaced exchangeable or solubilized calcium. We hypothesized that the formation of CaSO4 reduced the precipitation of P thereby increasing solution P. However, the chemical form of the precipitated P is unknown and there is no direct evidence for the presence CaSO4 in the soil. The proposed study will demonstrate the application of "state of the art" spectroscopic technique to finding practical solution of low phophorus fertilizer use efficiency. Our ability to identify and quantify the P minerals that are formed in a dual band will aid our efforts at finding the right formula for improving the fertilizer use efficiency of P by the crop. An increase in phosphorus fertilizer use efficiency will provide economic and environmental benefits for Canadian farmers through reduced input cost and reduced residual soil phosphorus.