Objective   NPK fertilization to maximize the yield and quality of chili peppers for processing was formulated. 【Method】 An experiment of quadratic saturation D-optimal design with three factors of nitrogen, phosphorus, and potassium was applied to optimize the formulation targeted to maximize the yield and quality of Mingjiao 9 chili peppers for further processing.

  Result   Significant effects on chili pepper yield and processing quality were found to be K＞P＞N. The optimal amount of N, P₂O₅, K₂O was 151.10, 59.28, 306.78 kg·hm⁻² to reach the greatest yield, and 148.59, 59.34, 291.66 kg·hm⁻² to achieve the most desirable quality. The combinations of N and P, N and K, and P and K also exerted significant enhancing effects on the chili pepper yield and quality. The optimized fertilizations with a predicted yield exceeding 29,000 kg·hm⁻² at 95% confidence level called for the application N, P₂O₅, and K₂O at 109.24–174.43 kg·hm⁻², 44.40–78.95 kg·hm⁻², and 213.85–287.95 kg·hm⁻², respectively, while for a score above 80 on overall chili pepper quality, the application of 63.08–115.23 kg·hm⁻², 42.26–72.50 kg·hm⁻², and 211.23–292.23 kg·hm⁻², respectively, were determined.

  Conclusion  Experimentally optimized NPK fertilizations for chili pepper cultivation to provide a yield of 29000 kg·hm⁻² and a quality score of 80 or higher were formulated. To accomplish the goal on yield as well as quality, the formulation would include the ranges of 109.24–115.23 kg·hm⁻² on N, 44.40–72.50 kg·hm⁻² on P₂O₅, and 213.85–287.95 kg·hm⁻² on K₂O with a N∶P₂O₅∶K₂O ratio of 1–1.05∶0.41–0.6∶1.96–2.64.