Non-Structural Carbohydrates Regulated by Nitrogen and Phosphorus Fertilization Varied with Organs and Fertilizer Levels in Moringa oleifera Seedlings

Moringa oleifera (moringa) is an important fodder tree species. Although several researches study the effects of fertilization on moringa growth, the response of non-structural carbohydrate (NSC) to nitrogen (N) and phosphorus (P) fertilization in moringa seedlings is poorly understood. Here, we employed a pot experiment to investigate the effects of N and P fertilization on NSC dynamics in moringa seedlings in southern China. The results showed that the moringa root NSCs were 427 mg g−1 in the control treatment (over 50% of the total NSCs, 739.8 mg g−1), while the leaf NSCs only stored about 10% of NSCs in the individual tree. Compared to the control treatment, the NSCs in leaf, stem, and root of moringa seedlings were greatly reduced by N and P fertilization, which could be explained by the dilution effects of increased biomass following fertilization. However, the magnitude of NSC change with fertilization varied with tissue and N & P application levels. Our results suggest that there is a trade-off between structural carbohydrates (SCs) and NSCs among different organs in morniga seedlings. As moringa seedlings may have specific nutrient acquiring strategies that differs from their adult tree, long-term and large-scale researches should focus on the effects and underlying mechanisms of fertilization on the trade-off between SC and NSC in seedling and the adult tree of moringa in future.