Lettuce (Lactuca sativa L.) growth, yield and quality response to nitrogen fertilization in a non-circulating hydroponic system

ABSTRACT

The objective of this study was to determine the effect of nitrogen fertilization rate on growth and quality of leafy lettuce grown during the winter season in non-circulating hydroponic system. Plants were subjected to seven nitrogen (N) concentrations, i.e. 0, 30, 60, 90, 120, 150 and 180 mg L⁻¹ N using ammonium nitrate. Nitrogen treatments did not have a significant effect on leaf fresh and dry mass, root fresh and dry mass, number leaves and leaf area. Leaf ascorbic acid and total phenolic content, and antioxidant capacity peaked at 100 and 120 mg L⁻¹ N, whereas leaf chlorophyll concentration linearly increased with increasing N application. The results indicate that a solution N concentration of 100 and 120 mg L⁻¹ may be sufficient to improve growth, yield and quality parameters of leafy lettuce grown in non-circulating hydroponic system.

KEYWORDS:

• Ascorbic acid
• chlorophyll
• leafy green
• nitrogen
• total phenols
• yield

Acknowledgments

The analysis of bioactive compounds was conducted at the Fruit and Vegetables Technology Laboratory, Department of Crop Sciences, Tshwane University of Technology (TUT) during this study. Authors wish to thank Ms. M.B. Mampholo for the technical assistance on experimentation during this study at the TUT.

Funding

The authors wish to express their profound gratitude to the Agricultural Research Council for financial support of the study.