Effects of planting density and fertilization on growth characters and artemisinin of Artemisia annua L.

Field plot trials were carried out to study the effects of different planting densities and fertilization levels on Artemisia annua growth, biomass allocation and artemisinin content. A. annua was grown at three densities, namely high density (111111 plants/ha), intermediate density (55555 plants/ha) and low density (27778 plants/ha). There were three levels of compound fertilizer (N-P2O5-K2O 15-15-15, 0, 60 and 120 kg/ha) for each density. The results show that A. annua is very flexible in response to the planting densities and nutrient availabilities, and the planting density is the main factor affecting the parameters related to the plant size, biomass allocation and yield, while artemisinin content is determined by the fertilizer levels. The biomass per plant, basal diameter and branch numbers of A.annua are significantly increased with the decrease of the planting density. The root mass fraction and ratio of the root mass to crown mass under the low planning density are significantly higher than those under the intermediate and high planting densities. In each planting density treatment, the biomasses per plant of A. annua are not significantly changed under the different fertilizer levels, while the biomass allocations of A. annua are significantly changed. Under the low planting density, the root mass fraction and root mass/crown mass are significantly increased with the decrease of the fertilizer levels, and under the high planting density, the leaf mass fractions are significantly increased with the increase of the fertilizer levels. Among all the treatments, the artemisinin content of A.annua is highest under the low planting density and the low fertilization, the leaf biomass and artemisinin yield are highest under the intermediate density and the low fertilization. In summary, the optimal density and fertilizer treatment are 55555 plants/ha and N 60 kg/ha in the experiment.