Yield and quality responses of Moringa oleifera Lam. to nitrogen fertilization

Moringa oleifera leaves are used for dietary purposes, as a vegetable and as medicine, in rural communities of South Africa. This demand is constantly increasing, therefore, the cultivation of cultivars with high leaf yields of good quality is essential. The application of nitrogen (N) to improve yield, as well as the medicinal quality of leaves is vital. Nitrogen applications to improve yield of moringa have been reported by several authors, however, without considering the effect of N on the medicinal quality of the leaves. The aim of this study, was to investigate different N levels (0 (control), 560, and 960 kg ha(-1) N) on yield and quality of 9-year-old M. oleifera trees at the Hatfield Experimental orchard of the University of Pretoria in South Africa. Two split applications were done in July and August 2014. Soil and leaf analyses were conducted before and after N applications. Yield and quality was determined by screening for the leaf extract yield, minimum inhibitory concentration (MIC) and total activity (leaf quality) of leaves before and after N was applied. Leaf chlorophyll content of each treatment was measured in 2-week intervals. Results from leaf extract yield, MIC, total activity, leaf chlorophyll and leaf N content readings showed that N influenced the response of M. oleifera trees. Leaf extract yield, leaf N and chlorophyll content increased with increasing levels of nitrogen applications of 0, 560, and 960 kg ha(-1) N, while the bioactivity (MIC) of leaves decreased with an increase in N levels. The increase in N might also increase the leaf protein content. Therefore, it is important to identify the type of protein that is influenced by the leaf nitrogen content.