Effects of Fertilization Frequency and Amount on the Chemometric Characteristics, Physiology, and Yield of Tomato Under Substrate Cultivation

This study examined the effects of fertilization frequency and quantity on growth, yield, and quality of tomatoes under substrate cultivation. A factorial experiment evaluated two fertilization frequencies (every 5 or 10 days) and three fertilization levels (15.69, 31.38, or 62.76 kg·ha⁻¹), along with an unfertilized control. Plants were assessed for growth and development, photosynthetic pigment content, gas exchange parameters, nutrient uptake, fruit quality attributes, and yield. Fertilization every 10 days at 62.76 kg·ha⁻¹ (T8) produced the highest nutrient content in both substrate and plant tissues. Compared with the control, fertilization every 5 days at 31.38 kg·ha⁻¹ (T4) significantly increased soluble sugar and soluble solids content in tomato fruits while decreasing organic acid content, without significantly affecting vitamin C content or yield. Comprehensive evaluation using five analytical methods-principal component analysis (PCA), VIKOR method, TOPSIS analysis, membership function analysis, and grey relational analysis-identified T4 as the optimal treatment demonstrating superior overall performance. These findings provide a theoretical basis and practical guidance for scientific fertilization management to achieve high-quality, high-yield, and sustainable tomato production under substrate cultivation systems. The results support precision nutrient management strategies for soilless vegetable production.