Impact of nitrogen supply on glucosinolate content and phenolic acids in cauliflower varieties

ABSTRACT

Application of nitrogen (N) is a common practice used to achieve profitable yields in horticultural crops and N application can be used as a tool to manipulate the enhancement of phytochemicals in vegetable crops to address consumer-oriented quality production. Our previous findings recommended 90 kg ha⁻¹ for certain types of cauliflower varieties without compromising yields. Thus, this study was aimed to investigate the effect of N application on glucosinolates and phenolic acids, at harvest, in varieties ‘Largardo’, ‘Eskimo’ and ‘CF-744’ grown in the field. N was applied as ammonium nitrate (NH₄NO₃) at concentrations from 0, 60, 90, 120, 150 to 180 kg ha⁻¹. Variety ‘CF-744’ was more sensitive to N supply and at 180 kg ha⁻¹ N it showed the highest accumulation of glucosinolates (sinigrin, glucoiberin, progoitrin, 4-methoxyglucobrassicin) at harvest. However, 90 kg ha⁻¹ N supply demonstrated the highest accumulation of majority of the glucosinolates in varieties ‘Largardo’ and ‘Eskimo’. Different varieties responded differently to N supply and glucosinolate levels in cauliflowers. Also, different varieties responded differently to N supply and antioxidant property. In all three varieties, the N supply at 120 kg ha⁻¹ showed the highest accumulation of protocatechoic acid, 4-hydroxy benzoic acid, ρ-coumaric acid and caffeic acid.

KEYWORDS:

• Antioxidant property
• bioactive compounds
• fertiliser application
• Glucoiberin
• sinigrin
• vegetable crop

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes on contributors

Madonna N. Mashabela obtained a doctoral degree and this manuscript emanated from her research findings that she carried out in her experimental work.

Martin Maboko, Ph.D., researcher in the field of horticulture. His fields of interest include the influence of nitrogen application rates on morphological parameters of vegetables grown in soil and hydroponic systems.

Puffy Soundy, Ph.D. His research interest is on the agronomy of vegetable crops.

Dharini Sivakumar, Ph.D. Her work is involved in the quality analysis, phytochemical and nutritional analysis.

Additional information

Funding

This study is based on research that was funded by the National Research Foundation (NRF) of South Africa (grant number 98352).