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• The increase of potassium(K) promoted total soluble sugar up to 38.3 % under 75 %Ep. • Low water combined with high nitrogen(N) and K achieved the largest irrigation water use efficiency. • The N and K contents in fruits significantly affected yield based on path analysis. • Medium water combined with high N and low K performed best in balancing yield, quality, and efficiency. Appropriate deficit irrigation and nutrient supply are key to efficient agricultural water use in arid and semi–arid regions. An experiment was conducted to evaluate the effects of the combined nitrogen and potassium application on the growth of cherry tomatoes under deficit irrigation across 2021 spring(S) and fall(F). A quadratic orthogonal rotation design with three factors and three levels was adopted, for the following treatments: irrigation levels of W1 (50 % evaporation(Ep)), W2 (75 % Ep), and W3 (100 % Ep); the nitrogen application levels of N1 (S:183.8 kg/ha, F:131.3 kg/ha), N2 (S:367.5 kg/ha, F:262.5 kg/ha), and N3 (S:551.3 kg/ha, F:393.8 kg/ha); and the potassium application levels of K1 (S:98.6 kg/ha, F:70.5 kg/ha), K2 (S:197.3 kg/ha, F:140.9 kg/ha), and K3 (S:295.9 kg/ha, F:211.3 kg/ha). The results revealed that increasing the nitrogen and potassium application significantly promoted the element accumulation in fruits under W1 application, with nitrogen content increasing by 31.6 % and 24.7 %, and potassium content increasing by 25.4 % and 53.7 % in the two study seasons, respectively. When W2 was applied, increased potassium application promoted a 36.2 % and 38.3 % increase in total soluble sugar in the two study seasons, respectively. Nitrate nitrogen residue in the soil showed a downward trend with the deepening of the soil layer. The increased application of nitrogen and potassium enhanced irrigation water use efficiency, but reduced the partial factor productivity of fertilizer. Correlation and path analyses revealed that the application of nitrogen and potassium significantly affected potassium content in fruits, yield, and nitrate nitrogen residue in the 0–15 cm soil layer. The nitrogen and potassium contents in fruits significantly affected yield, with maximum path coefficients of 0.768 and 0.352, respectively. A comprehensive evaluation system consisting of five indicators was constructed, and yield obtained the maximum combined weight of 0.390 and 0.330 in the two seasons, respectively. W2N3K1 exhibited the best balancing in yield, quality, and efficiency based on the TOPSIS model. The proposed strategy offers a theoretical basis for the water–use–efficient and sustainable production of cherry tomatoes in arid and semi–arid regions. [ABSTRACT FROM AUTHOR]