Department of Chemistry and Soil Chemistry, University of Navarra, 31080 Pamplona, Spain.
J Agric Food Chem. 2011 Mar 9;59(5):1900-8. doi: 10.1021/jf103962k. Epub 2011 Jan 21.
Hydroponic plant experiments demonstrated the efficiency of a type of humic acid-based water-insoluble phosphate fertilizers, named rhizosphere controlled fertilizers (RCF), to supply available phosphorus (P) to different plant species. This effect was well correlated to the root release of specific organic acids. In this context, the aims of this study are (i) to study the chemical nature of RCF using solid-state (31)P NMR and (ii) to evaluate the real efficiency of RCF matrix as a source of P for wheat plants cultivated in an alkaline and acid soil in comparison with traditional water-soluble (simple superphosphate, SSP) and water-insoluble (dicalcium phosphate, DCP) P fertilizers. The (31)P NMR study revealed the formation of multimetal (double and triple, MgZn and/or MgZnCa) phosphates associated with chelating groups of the humic acid through the formation of metal bridges. With regard to P fertilizer efficiency, the results obtained show that the RCF matrix produced higher plant yields than SSP in both types of soil, with DCP and the water-insoluble fraction from the RCF matrix (WI) exhibiting the best results in the alkaline soil. By contrast, in the acid soil, DCP showed very low efficiency, WI performed on a par with SSP, and RCF exhibited the highest efficiency, thus suggesting a protector effect of humic acid from soil fixation.
水培植物实验证明了一种基于腐植酸的难溶性磷酸盐肥料——根际控制肥料（RCF）的有效性，它可以为不同的植物物种提供有效磷（P）。这种效果与根系释放特定的有机酸密切相关。在这方面，本研究的目的是（i）使用固态（31）P NMR 研究 RCF 的化学性质，（ii）评估 RCF 基质作为 P 源的实际效率，与传统的水溶性（过磷酸钙，SSP）和难溶性（磷酸二钙，DCP）磷肥相比，在碱性和酸性土壤中种植小麦。（31）P NMR 研究表明，通过形成金属桥，腐植酸的螯合基团与多金属（双和三，MgZn 和/或 MgZnCa）磷酸盐形成了关联。关于磷肥效率，结果表明，RCF 基质在两种土壤中均比 SSP 产生更高的植物产量，DCP 和 RCF 的难溶性部分（WI）在碱性土壤中表现最佳。相比之下，在酸性土壤中，DCP 的效率非常低，WI 与 SSP 相当，而 RCF 的效率最高，这表明腐植酸具有防止土壤固定的保护作用。
