Context: Nitrogen (N) and potassium (K) are essential nutrients in intensive wheat production, but imbalanced fertilization compromises efficiency, yield, and environmental sustainability. Objective: This study aimed to elucidate the effects of N-K interactions on grain yield, plant nutrient requirements, nutrient use efficiency, and soil nutrient residues, with the goal of developing optimized fertilization strategies for sustainable agricultural production. Methods: A four-year field experiment was conducted with multiple wheat cultivars under contrasting N and K fertilization regimes. Grain yield and its components, nutrient uptake, nutrient use efficiency indices, and soil nutrient residues at maturity were measured. Results: N-K interactions indirectly enhancing grain yield (GY) by increasing the spikes per square meter (Spsm) and the number of grains per spike (Gnp). Combined N and K application stimulated nutrient demand, accumulation, and use efficiency; a synergistic effect was observed between N uptake efficiency (NUpE) and K uptake efficiency (KUpE). Regardless of N rate, higher K supply markedly reduced soil nitrate-N content (SNc) while increasing soil potassium content (SKc) and soil residual potassium (SRK) at maturity. Using the relationship between surface SNc and deep soil residual nitrate (SRN), optimal N rates were 124 kg ha-1 under low N conditions and 171 kg ha-1 under high N backgrounds, with corresponding K rates of 106 kg ha-1 and 138 kg ha-1; these combinations produced grain yields of 6.91 t ha-1 and 8.38 t ha-1, respectively. Conclusion: Combined N and K fertilization at 124 kg N/106 kg K2O ha-1 and 171 kg N/138 kg K2O ha-1 sustains high wheat yield while minimizing environmental risks. Implications or significance: The findings provide a practical fertilization and nitrate residue management strategy for wheat systems and benchmark data for next-generation N-K interaction models.