Effect of Different Culture Nutrient Solution EC on Carrot Top Growth and Nutritional Contents in a Closed–type Plant Factory System

Abstract

The production of crops in controlled environments is a growing sector of modern agriculture. The objective of this study was to determine the optimal concentration of culture nutrient solution for the production of carrot leaves in a closed-type plant factory. After sowing, seedlings at the two-true-leaf stage were transplanted to a growing bed system. Hydroponic cultivation was performed using a three-layer NFT system. Culture nutrient solutions were supplied at three electrical conductivity (EC) levels (2.0, 3.0, and 4.0 dS·m-1). Measurements of plant growth characteristics, including fresh weight, dry weight, plant height, and leaf area, were performed 14 and 23 days after planting. Differences in culture nutrient solution concentrations did not affect leaf number and chlorophyll content, and did not cause significant difference in antioxidant capacities and total phenol content of carrot plants. However, contents of total phenol, chlorogenic acid, and kaempferol were highest in plants grown in the EC 2.0 dS·m-1 solution, whereas those grown in the EC 3.0 dS·m-1 solution had the highest fresh and dry weights. Collectively, our results indicate that an EC 3.0 dS·m-1 culture nutrient solution combined with a cultivation period of 20-25 days is optimal for the hydroponic cultivation of carrot leaves in a controlled environment. In addition, we found that carrot leaves contain antioxidant compounds and are thus suitable as a leaf vegetable.