Response of yield and quality of cauliflower varieties (Brassica oleracea var. botrytis) to nitrogen supply

The fertilizer nitrogen (N) inputs to some vegetables such as cauliflower ( Brassica oleracea var. botrytis) can be large. One approach to decreasing t he input of N may be to select for cultivars efficient in the use of nitrog en. The objective of this investigation was to identify a cultivar which wa s nitrogen efficient in terms of producing a high yield under nitrogen (N) limiting conditions. Field trials were conducted in 1993 and 1994 with the cauliflower F-1-hybrids (B. oleracea var. botrytis) 'Marine', 'Lindurian' a nd 'Linford' at the Ruthe (Germany) and Schermer (the Netherlands) sites. O ptimum N supply was 250 kg ha(-1) as the sum of the inorganic N content of the soil (N-min) at planting and fertilizer N. Limiting N supply consisted of N-min, at planting and mineralization of N during cultivation. The N-min at planting was 116 and 66 kg ha(-1) at Ruthe and 84 and 20 kg ha(-1) at S chermer in 1993 and 1994, respectively. The yield in terms of total dry-mat ter and quality (measured as percentage class 1 curds) was highest with 'Ma rine' both at limiting and optimum N supply. Additionally, in quality 'Mari ne' was the least sensitive variety to N shortage. Thus,'Marine' could be r egarded as being nitrogen efficient. 'Linford' could be considered as nitro gen inefficient in quality, whereas 'Lindurian' generally performed inconsi stently. The reduction in quality with N shortage was due to an increase in loose curds, indicating that limiting N supply promoted the process of bol ting. Quality defect buttoning increased in part with N shortage. 'Marine' produced no buttoned curds. Bracting was not affected by N supply and appea red only in Ruthe 1993 with 'Lindurian' and 'Linford'. It was concluded tha t the improved efficiency with 'Marine' in terms of total dry matter and qu ality might have been achieved either through a higher N uptake capacity of the root system (uptake efficiency) and/or through a greater utilization o f nitrogen by the plant (N utilization efficiency).