Objective To study the effects of compound fertilizer application amount on yield, nutrient absorption and accumulation of main effective component oligosaccharides of Morinda officinalis, and provide a theoretical basis for the fertilization management of M. officinalis.

Method Using M. officinalis as the research object, through the pot experiment, a total of six treatments were set up to apply 0, 2, 4, 6, 8 and 10 g compound fertilizer (CK, T1, T2, T3, T4 and T5) per plant. The yield, nutrient content and oligosaccharide content of M. officinalis under different fertilization treatments were determined. Then we analyzed the correlation between the indicators, and comprehensively evaluated them by principal component analysis.

Result The application of compound fertilizer significantly improved the yield of M. officinalis, increased the N, P and K contents, and contributed to the increase in the accumulation of oligosaccharides. The highest yield and total oligosaccharide accumulation were achieved in the treatment of 6 g compound fertilizer per plant (T3), compared with no fertilizer (CK), with increases of 114.47% and 75.36% respectively. Fertilizer application reduced the oligosaccharide content of M. officinalis to some extent, with a maximum decrease of 35.65% compared to CK. The utilization efficiency of nutrient in compound fertilizer by M. officinalis showed N > K > P, and the accumulations of N, P and K in T3 treatment were higher than those of other treatments. The yield was the most critical factor affecting the accumulation of oligosaccharides in M. officinalis. The yield of M. officinalis was significantly or highly significantly positively correlated with the whole plant N, P, K contents and the accumulation of four oligosaccharides, but the contents of nystose and 1^F-fructofuranosyl nystose were significantly or highly significantly negatively correlated with the yield and the whole plant N, P, K contents. The comprehensive score of principal component analysis from high to low was T3>T5>T4>T2>T1>CK, with T3 treatment being the best.

Conclusion It is suggested that the cultivation of M. officinalis should focus on N fertilizer, and supplement K and P fertilizer appropriately. Proper fertilization can significantly increase the yield of M. officinalis and the accumulation of oligosaccharides.