Variety specific responses of cauliflower varieties (Brassica oleracea var. botrytis) to different N application rates on yield, colour and ascorbic acid content at harvest

The influence of five nitrogen (N) application rates (60, 90, 120, 150 and 180kgN/ha) were evaluated using limestone ammonium nitrate on the curd fresh and dry mass, size, chromaticity coordinates, L*, a*, b* and ascorbic acid content in cauliflower varieties (Largardo, Eskimo and CF-744) during the 2015 and 2016 seasons. Commercial standard 120kgN/ha was included as a control. Variety Largardo' showed weak response to N application rates and can be regarded as the least sensitive variety for lower N use. Curd fresh and dry mass and size were not affected at lower N application rates of 60 and 90kg/ha in Largardo' compared to the other two varieties. However, L*, b* colour value and ascorbic acid content was higher at lower N application rates <90kgN/ha in all three varieties. With increasing N application rates, curd became darker and less intense in yellow colour. Increasing rates of N application clearly posed a negative effect on ascorbic acid content. Therefore, Largardo' can be recommended as a suitable variety that produces higher yield and ascorbic acid content at 60 or 90kgN/ha, with the application rates lower than the commercially recommended rate (120kgN/ha).