Effects and optimization of different NPK ratios on yield and quality of soilless cultivated cherry tomatoes

Protected soilless production and rapid cultivar upgrading have altered the macronutrient requirements of cherry tomato, increasing the need for nutrient solution optimization. In this study, nitrogen (N), phosphorus (P), and potassium (K) (expressed as P2O5 and K2O equivalents, mg L−1) were optimized using a three-factor, five-level central composite design (CCD) combined with response surface methodology (RSM), with yield per plant and total soluble solids (TSS) as response variables. The quadratic models adequately described both responses, with R2 values of 0.9676 for yield and 0.8772 for TSS. K2O showed the strongest effect on yield (F = 153.50, p < 0.0001) and TSS (F = 37.01, p = 0.0005), while a significant P2O5 × K2O interaction affected yield (p = 0.0383). Multi-response optimization identified TB (N 290, P2O5 120, and K2O 315 mg L−1) as the optimal formulation. In the validation experiment, TB increased yield per plant to 2,022 g, 11.7% higher than the Yamazaki control, and increased TSS to 7.48 °Brix. Compared with the control, TB also improved several additional fruit-quality traits. These results indicate that CCD–RSM is effective for optimizing macronutrient composition in soilless cherry tomato under the tested conditions.