Nitrogen and potassium are the two most essential elements for the growth of sweet potatoes. A balanced nitrogen and potassium supply is crucial for producing high-quality, high-yield sweet potatoes. This study aimed to establish an optimal nitrogen-to-potassium ratio model for diagnosing the nitrogen-to-potassium balance in sweet potato, and to achieve quantitative management of nitrogen and potassium fertilizers in sweet potato cultivation. The experimental design comprised four potassium levels (K0: 0, K1: 100, K2: 200, K3: 300 kg/ha) and four nitrogen levels (N0: 0, N1: 60, N2: 120, N3: 180 kg/ha). Biomass and nitrogen and potassium content were determined in different sweet potato organs. Bayesian modeling was employed to construct the critical plant nitrogen concentration models under varying potassium levels and the critical plant potassium concentration models under varying nitrogen levels. The results established critical nutrient concentration models for sweet potato: Nc = 3.31 DW−0.46 and Kc = 3.39 DW−0.47 for nitrogen and potassium, respectively. Furthermore, the critical N/K ratio was modeled as Nc/Kc = 0.976 DW0.01. Using independent experimental data from 2020, the nitrogen–potassium nutritional balance in plants was diagnosed based on the ratio of the measured N/K ratio to the critical N/K ratio. The results demonstrated that the model exhibited satisfactory predictive performance. Accordingly, the model enables quantitative diagnosis of the in-plant N/K ratio, offering a valuable tool for assessing nutrient balance in sweet potato and providing a theoretical foundation for precise nitrogen and potassium fertilization.
Zhao et al. (2026) studied this question.