Optimizing Nitrogen, Phosphorus, and Potassium Fertilization Levels for Container Plants of Lagerstroemia Indica ‘Whit III’ Based on the Comprehensive Quality Evaluation

To improve plant quality and fertilizing efficiency, we conducted a study to elucidate the effects of nitrogen (N), phosphorous (P), and potassium (K) fertilizers on the growth, nutrient accumulation, and quality of Lagerstroemia indica plants grown in containers and determine the optimal fertilization levels. Both single-factor and multifactor experiments involving N, P, K fertilizers were designed. Integrated with the plant growth, physiological traits, nutrient levels, and other indices, we used a membership function analysis to comprehensively evaluate plant quality. During the single-factor experiments, the best levels of the single fertilizers applied were 8 g/plant N, 2 g/plant P, and 4 g/plant K. We also found that, within a certain range, N, P, and K fertilizers promoted vegetative growth, increased the chlorophyll, soluble sugar, and soluble protein concentrations, and enhanced nutrient accumulation of L. indica . To avoid the wasting of fertilizers and promote plant quality, the optimal application levels were calculated using a regression analysis. The suggested N, P, and K applications were 6.89 g/plant, 1.97 g/plant, and 3.33 g/plant, respectively. Our results revealed that N, P, and K effect the performance of L. indica container plants, which paves the way for developing reliable and precise fertilizing techniques for growing L. indica .