[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.