Potassium Chloride-Modified Urea Phosphate with Response Surface Optimization and Its Application Effect on Maize in Saline-Alkali Soil

Guiting Yang; Hongmeng Zhao; Qi Chen; Xiaojing Yu; Zeli Li; Kexin Liu; Min Zhang; Zhiguang Liu

doi:10.1021/acsomega.0c01428

Potassium Chloride-Modified Urea Phosphate with Response Surface Optimization and Its Application Effect on Maize in Saline-Alkali Soil

ACS Omega. 2020 Jul 7;5(28):17255-17265. doi: 10.1021/acsomega.0c01428. eCollection 2020 Jul 21.

Authors

Guiting Yang¹, Hongmeng Zhao¹, Qi Chen¹, Xiaojing Yu¹, Zeli Li¹, Kexin Liu², Min Zhang^{1

3}, Zhiguang Liu^{1

3}

Affiliations

¹ 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.
² Department of Environmental Engineering Sciences, University of Florida, Gainesville, Florida 32611, United States.
³ State Key Laboratory for the Integrated Use of Nutritional Resources, Kingenta Ecological Engineering Group Ltd., Linshu, Shandong 276700, China.

Abstract

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 K₂O 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 K₂O value content and UPK yield were 3.51% and 69.8%, respectively. The experimental K₂O 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 K₂O 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.