Effects of phosphorus application rate on the growth and quality of Artemisia argyi

Objective Chinese mugwort (Artemisia argyi) is an important herb resource, and meeting the high demand for it heavily relies on establishing an artificial plantation. In this paper, we studied the effects of phosphorous (P) fertilizer application rate on the growth and quality of mugwort (A. argyi).

Methods Field experiments were conducted in the main production base of Chinese mugwort (A. argyi) in Qichun, Hubei Province. Newly transplanted seedlings and regenerated seedlings of mugwort were tested in 2018 and 2019, respectively. The P₂O₅ rate treatments included 0, 60, 120, 180, and 240 kg/hm² (i.e., P₀, P₆₀, P₁₂₀, P₁₈₀ and P₂₄₀, respectively). The agronomic characteristics, leaf yield and the output rate of moxa were measured. Mineral contents, total volatile oil, volatile components, flavonoids and phenolic acids in A. argyi leaves were determined.

Results The application of P fertilizer significantly increased the leaf yield of A. argyi but not the agronomic characteristics. There was no significant difference in the leaf yield of the four P rate treatments in 2018, and P₁₂₀, P180 and P₂₄₀ treatments recorded a similar leaf yield in 2019. According to the fitted curve, the highest leaf yield of A. argyi was recorded at P 166.5 kg/hm² in 2018 and 157.7 kg/hm² in 2019. P application increased the uptake of N, P and Ca, but not Mg and Zn, and decreased that of Cu. P application significantly increased the output rate of moxa. The highest moxa yield was obtained at P₁₈₀ and P₁₂₀ treatments in 2018 and 2019, which were 21.0% and 12.3% higher than that in P₀ treatment. According to the fitted curve, the P rate promoting the highest output was P₂O₅ 140.2 kg/hm² in 2018 and 165.0 kg/hm² in 2019. Total volatile oil, eucalyptus oil, and 8 kinds of flavonoids and phenolic acids found in A. argyi leaves were significantly increased by applying P fertilizer. However, the contents of α-thujone and camphor decreased with an increase in P fertilizer application. Principal component analysis was conducted on 14 quality indexes of A. argyi leaves under different P application rates in two years. Three principal components were extracted in the 2018 experiment, whose cumulative contribution rate was 98.9%, and two principal components were extracted in the 2019 experiment, whose cumulative contribution rate was 92.6%. The total score showed that the quality of A. argyi leaves treated with P₁₂₀ and P₁₈₀ treatments was higher than taht of other treatments, and the quality of A. argyi leaves treated with P₀ treatment was the lowest.

Conclusions The application rate of P fertilizer affect the growth, leaf yield and quality of mugwort (A. argyi.). Under the experimental condition in Qichun, a reasonable P fertilizer application rate could substantially increase the output of moxa and the ratio of components in the total volatile oil of mugwort. The highest leaf yield was recorded at P₂O₅ 180 kg/hm² for newly transplanted mugwort and 120 kg/hm² for regenerated mugwort. A high comprehensive score of mugwort corresponds to high P fertilizer use efficiency.