Selected yield and qualitative parameters of broccoli in dependence on nitrogen, sulfur, and zinc fertilization

The effect of nitrogen (N), sulfur (S), and zinc (Zn) fertilization on the yield quantity and selected qualitative parameters of broccoli was studied in an experiment carried out in Nitra (Slovak Republic) during 2011 and 2012. In this experiment, the following fertilization treatments were tested: control; N200S80 (fertilized to the supply level: 200 kg N ha(-1) and 80 kg S ha(-1)); N-200 S-100 (supply level: 200 kg N ha(-1) and 100 kg S ha(-1)), and N200S100Zn (supply level: 200 kg N ha(-1) and 100 kg S ha(-1) + foliar zinc application). Compared to the control treatment, higher broccoli yield was shown at all fertilized treatments. The most significant increase in yield quantity was found at N200S100Zn, i.e. about 59% higher than the control. Application of N200S100Zn was the most suitable fertilization from the standpoint of broccoli quality. The foliar Zn spraying led to a statistically highly significant increase of sulforaphane in broccoli (about 41.1%) compared to the control. The applied N and S fertilization tended to decrease the vitamin C content in broccoli (about 9.2%) against the control. On the other hand, Zn application resulted in a return of the vitamin C content, nearly to its level in control. The results confirmed the well-known fact that nitrogen fertilization leads to nitrate accumulation in vegetables. However, the results of this research indicate that nitrogen fertilization combined with zinc application should be expressed mainly by lower nitrate accumulation in the edible parts of broccoli. The experimental data are interesting, and in terms of growing vegetables for consumption with enhanced quality, promising. This is notable because the formation of many serious diseases is increasing.