Effects of nitrogen application rate and harvest time on yield and quality of Artemisia argyi H. Lév. & Vanio at different stubble periods

Artemisia argyi, also known as silver wormwood or Chinese mugwort. To establish a nitrogen fertilizer application and harvesting management system for multiple harvests of Artemisia argyi, this study combined 3 stubble periods, 4 nitrogen application rates, and 3 harvest times, with 12 treatments for the first crop, 15 treatments for the second crop, and 21 treatments for the third crop, and systematically analyzed the yield and quality of Artemisia argyi leaves. The results showed that the yield of Artemisia argyi leaves in the three stubble periods was in the order of the first crop > the second crop > the third crop. The overall quality of the first crop leaves was the best; the second crop leaves had a higher output rate of moxa; and the third crop leaves had higher contents of chlorogenic acid, neochlorogenic acid, and cryptochlorogenic acid. Compared with the no-nitrogen application treatment, the “0.67 g·pot⁻¹ (268 kg·ha⁻¹) nitrogen application in the first crop + 0.67 g·pot⁻¹ (268 kg·ha⁻¹) nitrogen application in the second crop + no nitrogen application in the third crop” system increased the yield and quality of Artemisia argyi leaves in each stubble period and overall. Principal component analysis revealed that the first crop Artemisia argyi should be harvested 75 days after the sixth true-leaf stage. The optimal harvest time for the best quality under nitrogen application was 7 days earlier than that under no nitrogen application, and this harvest time significantly increased the yield and quality of Artemisia argyi leaves of the second and third crops (P < 0.05). Additionally, excessive nitrogen application would reduce the yield of Artemisia argyi leaves and affect their quality. In conclusion, optimizing the nitrogen application rates and harvest time for different stubble periods can effectively improve the quality and yield of Artemisia argyi leaves.