Growth of Astragalus membranaceus during nursery period as affected by different plug tray cell size, number of seeds per cell, irrigation interval, and EC level of nutrient solution

Abstract

The present study aimed to evaluate seedling quality of Astragalus membranaceus as affected by different plug tray cell size, number of seeds per cell, irrigation interval, and EC (electrical conductivity) level of nutrient solution to establish the optimal plug seedling method of A. membranaceus. For plug cell size and the number of seeds per cell treatments, 128, 200, and 288-cell plug trays were used, and 1, 2, and 3 seeds were sown in each cell in a 128-cell plug tray. Irrigation time and interval were set at 1, 2, and 3 minutes and 1 day interval, 2 days interval, and 3 days interval, respectively. The EC level of nutrient solution was set at 6 levels of 1.0, 1.5, 2.0, 2.5, 3.0, and 3.5 dS∙m-1. The seedling growth of A. membranaceus was the greatest in the 128-cell plug tray with one seed sown per cell. As concerns the irrigation interval and time, leaf area and fresh weights of shoot and root were significantly the highest in the irrigation at the interval of once a day for two minutes. The EC level of nutrient solution was the greatest in 2.0 dS∙m-1, and the seedling growth decreased when the EC level of nutrient solution was higher than 2.5 dS∙m-1. These results suggest that the optimal plug seedling method of A. membranaceus is sowing two seeds per cell using a 128-cell plug tray and supplementary planting after germination, with the irrigation at one-day interval for 2 minutes with the EC level of 2.0 dS∙m-1.