Nitrogen and Potassium in Nutrient Solution Influence Seedling Growth of Four Vegetable Species

Abstract

Abstract Broccoli (Brassica oleracea L. var. Italica), celery (Apium graveolens L.), lettuce (Lactuca sativa L.), and pepper (Capsicum annuum L.) seedlings were grown in multicells and fertilized with complete nutrient solutions at two N rates (150 or 350 mg·liter−1) and three K rates (50, 200, or 350 mg·liter−1) in factorial combination. Shoot growth of all species was enhanced at higher N rates but root growth decreased. Broccoli leaf area and shoot dry weight increased curvilinearly with K rate with a maximum at 200 mg·liter−1. For celery K rates increased leaf area linearly. The effect of K rates on growth characteristics was generally a function of the N status and differed among species, celery being the least affected. Under the high N rate, maximum percentage of shoot dry matter, root dry weight, and root:shoot dry weight ratio, as well as minimum specific leaf area of broccoli were obtained with the intermediate K rate. Increasing K rates under high N status enhanced both lettuce leaf area and dry matter accumulation. For pepper, this caused leaf expansion and resulted in more succulent plants.