The appropriate nitrogen fertilization rate to enhance Artemisia argyi yield and quality

Objectives Nitrogen (N) fertilization affects the growth, yield and quality of Artemisia argyi. We investigated the optimal N application rate for high yield and quality to provide a scientific basis for standardized N fertilization of A. argyi in Qichun.

Methods Two field experiments were conducted at the experimental base of A. argyi in Qichun, Hubei Province, from 2018 to 2019. The first field was newly planted, and the second was continuously planted with A. argyi. We used P₂O₅ 120 kg/hm² and K₂O 120 kg/hm² as the basis to set up five N (urea) application rates of 0, 60, 120, 180 and 240 kg/hm². The agronomic traits, yield, leaf quality and N use efficiency of A. argyi were studied.

Results The growth of A. argyi was sensitive to N application rate. The emergence number and leaf yield of A. argyi reached the peak at N 168 kg/hm² and N 172 kg/hm² in 2018 and 2019, respectively. The corresponding maximum leaf yield was 7 030 kg/hm² and 6 200 kg/hm². Higher N application rate increased N and Cu contents in A. argyi leaves, while the K and Mg contents were the highest at N₆₀ and N₁₂₀, respectively. The P content was the highest at N₂₄₀. The highest moxa yield of A. argyi (1 743 kg/hm² in 2018 and 1 426 kg/hm² in 2019) was obtained at N 147 kg/hm² and N 142 kg/hm², respectively. The total volatile oil and its components, β-eugenone and caryophyllin, increased continuously. The contents of eucalyptol, α-platycladone, camphor, borneol and α-caryophyllene reached the highest at N 180 kg/hm². The highest phenolic acids and flavonoids contents were obtained at N 60−120 kg/hm². In addition, N partial productivity, N absorption rate, and N agronomic efficiency of A. argyi leaves showed a decreasing trend with the increasing N application rate.

Conclusions The yield and quality response of A. argyi to N fertilizer application rate were the same in new and old fields. The N application rate for the highest yield was N 170 (168−172) kg/hm², N 144 (141−147) kg/hm² for the highest moxa yield, N 180 kg/hm² for the highest volatile oil contents, and N 60−120 kg/hm² for the highest phenolic acids and flavonoids contents.