Lowering Nitrogen and Increasing Potassium Application Level Can Improve the Yield and Quality of Panax notoginseng
Xiaohong Ou, Xiuming Cui, Duanwei Zhu, Lanping Guo, Dahui Liu, Ye Yang
Abstract
Excessive nitrogen (N) application and potassium (K) supplement deficiency is a common problem in Panax notoginseng cultivation. However, synergistic effects of lowering N and increasing K application on yield and quality of P. notoginseng have not been reported. Field experiments in two locations with different N and K combined application were conducted to study the effects on yield and quality. Then, the saponin accumulation mechanisms were explored by pot and hydroponic culture with 2- or 3-year-old seedlings. The investigation showed that 70% of P. notoginseng cultivation fields reached abundant levels of total nitrogen (TN) but had deficient levels of total potassium (TK), which may be detrimental to balance the N/K uptake of P. notoginseng . Moreover, the average biomass was 18.9 g, and P. notoginseng saponin (PNS) content was 6.95%; both were influenced by the N/K values of P. notoginseng . The field experiments indicated that compared to the conventional N and K application (N:K = 2:1), lowering N and increasing K application (N:K = 1:2) decreased root rot rate by 36.4–46.1% and increased survival rate, root biomass, and yield, as well as PNS content by 17.9–18.3, 5.7–32.9, 27.8–57.1, and 5–10%, respectively. The mechanism of lowering N and increasing K application on the PNS content improving was due to the decreasing of N/K value, which promoted photosynthesis, sugar accumulation, and the expression of saponin biosynthesis genes. Therefore, lowering N and increasing K application to the ratio of 1:2 would have great potential to improve the synergistic effect on yield and quality of P. notoginseng cultivation.