Adjustable N:P2O5 Ratio Urea Phosphate Fertilizers for Sustainable Phosphorus and Nitrogen Use: Liquid Phase Equilibria via Solubility Measurements and Raman Spectroscopy

Abstract

Design and use of the adjustable N:P2O5 ratio fertilizers is crucial in proper nutrient management if sustainable phosphorus use is to be ensured. Overfertilization with phosphorus can lead to its fixation in soil, as well as the unwanted environmental phenomena, such as eutrophication. Urea phosphate, CO(NH2)2·H3PO4, based liquid fertilizers were synthesized in this work, and their resulting physicochemical properties were determined. For this purpose, phase composition information on the CO(NH2)2·H3PO4–CO(NH2)2–H2O ternary system was analyzed, and critical points on the polytherm were determined. Liquid fertilizer compositions were determined and their corresponding physicochemical properties established. Raman spectroscopy showed that CO(NH2)2·H3PO4 partially retains its strong bonding interactions between both molecular adducts in aqueous solutions suggesting their improved nitrogen management efficiency in soils. Effect of these acidic pH fertilizer solutions on the pH of soil was determined and was found negligible. The potential of these fertilizers for reducing the loss of nitrogen from the wet soil is also discussed.