Optimum nitrogen, phosphorus and potassium combination increasesthe rhizome yield and saponin content of Paris polyphylla

Objectives The effect of nitrogen (N), phosphorus (P), potassium (K) fertilizer levels on the yield and the saponin content of Paris polyphylla was studied, so as to propose a fertilizer formula for the efficient artificial cultivation.

Methods A Paris polyphylla field experiment was conducted in Chinese fir and bamboo mixed forest in Nanping City of Fujian Province, using “3414” experiment design. The N 270 kg/hm², P₂O₅ 375 kg/hm², and K₂O 300 kg/hm² were defined as level“2”, the 0.5 and 1.5 times of level 2 amount were defined as level “1” (insufficient) and level “3” (superfluous), respectively, and total of 14 fertilizer combination treatments were formed. At the harvest period of P. polyphylla, the plant morphology, rhizome yield, and the content of four saponins components in rhizomes were measured, and the production efficiency was calculated.

Results Application amount of N, P, and K fertilizers significantly affected the plant morphology, rhizome yield and saponin content of P. polyphylla, the contribution rates of N, P, and K fertilizer to rhizome yield were 59.75%, 27.54%, and 63.15%, respectively, with the highest contribution by K and lowest by P fertilizer. At N1 level, increase P and K levels decreased the plant height, stem diameter and leaf length. Treatments at N3 level were recorded the highest plant height and leaf length, but lower stem diameter than the treatments at N1 and N2 levels, indicating the importance of suitable N level for plant growth. The N, P, and K fertilizers showed interaction on the rhizome yield and saponin content. N₂P₂K₃ and N₂P₂K₂ combination were recorded significantly higher rhizome yields than the other combinations, and N₂P₂K₃ combination was tested the highest saponin content (1.62%). As a result, N₂P₂K₃ achieved the highest production benefit, followed by N₂P₂K₂.

Conclusions Appropriate levels of nitrogen and phosphorus fertilizer combined with relatively high level of K fertilizer favors the growth and saponin accumulation in rhizomes of P. polyphylla, therefore, N, P₂O₅, and K₂O combination amount of 270, 375, and 450 kg/hm² is recommended for the high quality and efficient P. polyphylla production in the tested area.