<p>This study investigated the effects of soil-applied, foliar-applied, and nano-potassium fertilization on nutrient uptake and content in maize (Zea mays L.). A pot experiment was conducted to evaluate conventional and nano-K fertilizers at recommended, half, and double rates, as well as integrated combinations. The results demonstrated significant improvements in plant nutrient content under all potassium treatments compared with the unfertilized control. Nitrogen content increased markedly, with the highest level observed in the double-rate nano-potassium treatment (T9, 1.77%), representing a 131% increase over the control. Integrated and combined fertilization treatments (T6–T8) also enhanced nitrogen content (1.667–1.71%, 117–123% increase). Phosphorus content was highest under nano-potassium at the recommended rate (T4, 0.611%), and combined or integrated treatments further improved P uptake. Potassium accumulation peaked under conventional soil application (T2, 2.18%), while nano-potassium treatments provided a more balanced nutrient uptake and improved efficiency. The observed enhancements in nutrient content are attributed to the synergistic roles of potassium in activating enzymatic processes, improving root development, and facilitating nutrient translocation, which collectively optimize nitrogen and phosphorus assimilation. These findings highlight the potential of nano-potassium fertilizers, especially when applied in integrated strategies, to increase nutrient-use efficiency and reduce total fertilizer inputs. The study supports the application of nano-K as a sustainable alternative to conventional potassium sources, offering opportunities for improved maize productivity and sustainable nutrient management.</p>