Yang Guiting, Zhao Hongmeng, Chen Qi, Yu Xiaojing, Li Zeli, Liu Kexin, Zhang Min, Liu Zhiguang
National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, National Engineering & Technology Research Center for Slow and Controlled Release Fertilizers, College of Resources and Environment, Shandong Agricultural University, Tai'an, Shandong 271018, China.
Department of Environmental Engineering Sciences, University of Florida, Gainesville, Florida 32611, United States.
ACS Omega. 2020 Jul 7;5(28):17255-17265. doi: 10.1021/acsomega.0c01428. eCollection 2020 Jul 21.
Urea phosphate (UP) is an acidic compound fertilizer, which significantly improves the low efficiency of P application caused by high pH in saline-alkali soil. In this study, urea phosphate potassium (UPK) was prepared by adding potassium chloride (KCl) to modify urea phosphate (UP) and the optimal combination of the synthetic process parameters was obtained using the response surface methodology at a four-variable, three-level experiment Box-Behnken design. Parameters such as the reaction temperature, KCl molar number, reaction time, and concentration of phosphoric acid were included for optimization. The thermostability, crystal structure, and microscopic morphology of UPK were measured by thermogravimetric analysis (TGA), X-ray diffraction (XRD), and scanning electron microscopy (SEM), respectively. The fertilizer efficiency was validated in an experiment on maize grown in pots containing saline-alkali soil. The highest KO content and UPK yield were obtained by using the following parameters: reaction time of 60 min, KCl of 0.32 mol, reaction temperature of 78 °C, and phosphoric acid concentration of 70%. Under optimal conditions, the predicted KO value content and UPK yield were 3.51% and 69.8%, respectively. The experimental KO content and UPK yield were 3.42 ± 0.35% and 67.58 ± 1.25%, respectively, which confirmed the strength of the predicted model. This model can be used as an effective tool to predict the KO content and yield in UPK. Characterizations showed that KCl was uniformly distributed in UPK and its fluidity was effectively improved as observed in the angle-of-repose results. Compared to a conventional phosphorus fertilizer diammonium phosphate (DAP), the yield, total P use efficiency, soil available phosphorus content, and soil acid phosphatase activity of UPK increased significantly by 25.58, 174.5, 24.41, and 41.25%, respectively, and the soil pH on UPK treatments decreased by 3.98% significantly. In conclusion, this novel technology to modify UP by using KCl has an enormous potential for large-scale applications to satisfy the increasing demand for UP fertilizers on saline-alkali soil.
磷酸脲（UP）是一种酸性复合肥料，它能显著改善盐碱地高pH值导致的磷肥施用效率低下的问题。在本研究中，通过添加氯化钾（KCl）对磷酸脲（UP）进行改性制备了磷酸脲钾（UPK），并采用响应面法在四变量、三水平的实验Box-Behnken设计中获得了合成工艺参数的最佳组合。优化参数包括反应温度、KCl摩尔数、反应时间和磷酸浓度。分别通过热重分析（TGA）、X射线衍射（XRD）和扫描电子显微镜（SEM）对UPK的热稳定性、晶体结构和微观形态进行了测定。在含有盐碱土的盆栽玉米实验中验证了肥料效率。通过以下参数获得了最高的KO含量和UPK产量：反应时间60分钟、KCl 0.32摩尔、反应温度78℃和磷酸浓度70%。在最佳条件下，预测的KO值含量和UPK产量分别为3.51%和69.8%。实验得到的KO含量和UPK产量分别为3.42±0.35%和67.58±1.25%，这证实了预测模型的可靠性。该模型可作为预测UPK中KO含量和产量的有效工具。表征结果表明，KCl在UPK中均匀分布，休止角结果表明其流动性得到了有效改善。与传统磷肥磷酸二铵（DAP）相比，UPK的产量、总磷利用效率、土壤有效磷含量和土壤酸性磷酸酶活性分别显著提高了25.58%、174.
