Abstract: Moringa oleiferahas important economic value. The availability of soil water and nitrogen is of great significance for their growth. In this study, we examined the coupling effects of soil water and nitrogen addition on the growth and biomass accumulation of Moringa oleifera ‘PKM I’ in the greenhouse of the Experimental Base of Ecology Teaching, College of Resources and Environment, South China Agricultural University. There were three water levels, including 40% (W1), 60% (W2), 80% (W3) of field water holding capacity, and four nitrogen levels, including 0 g·plant^-1 (N0), 0.6 g·plant^-1 (N1), 1.8 g·plant^-1 (N2), and 3.6 g·plant^-1 (N3), resulting in 12 treatments. The results showed that: (1) The height and basal diameter of Moringa oleifera-under low N level (N1) were generally higher than those under other treatments, whereas high N and W levels inhibited growth. (2) With respect to the branching pattern, under low W level, the branch length at each level, the overall branching rate, and the stepwise branching rate decreased with increased N fertilization level. The medium N fertilization following the higher W level was optimal for the fast growth of Moringa oleifera. (3) The biomass of Moringa oleiferadecreased under the high N level. Under no N addition, the biomass of Moringa oleiferawould decrease with the increasing W level. (4) In terms of comprehensive morphology, the W1N3 treatment significantly increased the root/shoot ratio (R/S). The slenderness index (SI) under W2N2 treatment was the lowest, indicating the best growth quality. Bulk index (BI) under the medium N level was higher than under other treatments, with the highest value under the W2N1 treatment. The Dickson quality index (DQI) under W2N2 treatment was the highest. These results suggest that suitable combination of water and N fertilizer could efficiently enhance the growth and biomass accumulation of Moringa oleifera.

Key words: Moringa oleifera, water and nitrogen coupling, growth, biomass, comprehensive morphology.