[Optimizing fertilization scheme of N, P2O5 and K2O concentration for eggplant under soilless culture]

To get optimal nitrogen (N), phosphorus (P₂O₅) and potassium (K₂O) concentrations range for high quality and yield of eggplant with vermiculite as cultivation substrate, three factors and quadratic saturation D-optimal regression (310) were used to establish a ternary quadratic mathematical model with N, P₂O₅ and K₂O concentrations as independent variables and eggplant yield and quality as objective functions. The results showed that yield and quality of eggplants were significantly influenced by N, P₂O₅ and K₂O concentrations. The yield was most influenced by K₂O concentration, and followed by N and then P₂O₅. The quality was also most influenced by K₂O concentration, and followed by P₂O₅ and then N. There were significant interactive effects of N+P₂O₅, N+K₂O and P₂O₅+K₂O on yield, and significant interaction of N+K₂O on eggplant quality. Under lower concentrations, the yield and quality of eggplants enhanced with the increasing N, P₂O₅ and K₂O concentrations. When the nutrient concentrations exceeded a threshold, both yield and quality decreased. According to computer simulations, the yield could reach to 3600 g·plant^-1 when the fertilization schemes were N 16.0-20.0 mmol·L^-1, P₂O₅ 2.2-2.6 mmol·L^-1 and K₂O 9.9-12.9 mmol·L^-1; the fertilization scheme needed to obtain a comprehensive quality score of higher than 90 were N 18.0-21.1 mmol·L^-1, P₂O₅ 1.9-2.6 mmol·L^-1 and K₂O 10.6-13.3 mmol·L^-1. In summary, fertilization scheme of high yield (43.2 kg·plot^-1) and high quality(comprehensive score of higher than 90) of eggplants were N 18.0-20.0 mmol·L^-1, P₂O₅ 2.2-2.6 mmol·L^-1, K₂O 10.6-12.9 mmol·L^-1, with an appropriate N, P₂O₅ and K₂O proportion of 1:0.13:0.62.