With increasing supply of S and N, the S and N concentra- tions as well as the N : S ratio in broccoli florets changed
0.2 1.0 –7.86a 10.89a 10.89a
0.6 1.0 –8.04a 10.56a 10.56a
1.0 1.0 –7.78a 10.43a 10.43a
0.2 4.0 –8.34ab 10.33a 10.33a
0.6 4.0 –8.74b 10.33a 10.33a
1.0 4.0 –8.84b 10.58a 10.58a
HSD 0.70 1.41 0.99
The color values L*, b*, and color saturation C*, as well as the hue angle of the broccoli heads did not differ significantly as their variability was quite high. Especially the broccoli plants subjected to insufficient S supply showed a strong non- homogeneity of the single heads in their yellow color (value b* minimum 7.7 – maximum 19.3). The color differences between broccoli heads may be explained by reduced chlorophyll concentration that is associated with S deficiency as reported for spinach (Dietz, 1989). However, as the outer product quality is very strongly determined by the head color due to consumers preferring very green broccoli, yellow values do not correspond to consumer preference (Schonhof et al., 2004).
Our findings of reduced yields with limiting N and S supply are in line with the body of evidence from other studies. Hence, at harvest time, the head weight differed as a conse- quence of the amount of N and S supplied. Plants receiving an optimal amount of N had a higher average head weight (213.89 ± 22.75 g) as compared to those supplied with an insufficient amount of N (72.60 ± 8.33 g) (Fig. 1).
(Tab. 2). In general, plants receiving an optimal N supply had
significantly lower S concentrations (6.04 2.56 g (kg DM)–1)
than those with insufficient N supply (9.54 ± 2.12 g (kg DM)–1).
The reduction of S supply led to a decrease of the S concentrations. The decrease was strongest for those plants having an optimal N supply in combination with insuffi- cient S supply (0.2 g).
Sulfur concentrations were reduced by
63% as compared to optimal S supply (0.6 g) and by 68%
with respect to excessive S supply (1.0 g S) (Tab. 2).