## 3 Results and Discussion
### Trace Element Contents in Brassicaceae Species: Conventional Versus Organic
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **Co (\(\upmu\)g/g)** & **Cr (\(\upmu\)g/g)** & **Cu (\(\upmu\)g/g)** & **Fe (\(\upmu\)g/g)** & **Mn (\(\upmu\)g/g)** & **Zn (\(\upmu\)g/g)** \\ \hline \multicolumn{6}{c}{**Conventional**} \\ \hline
**Farm I** & & & & & \\ \hline _Brassica rapa_ (turnip greens) & 0.23 \(\pm\) 0.10 & 2.41 \(\pm\) 1.50 & 11.3 \(\pm\) 3.8 & 223 \(\pm\) 133 & 56.0 \(\pm\) 20.1 & 38.9 \(\pm\) 23.1 \\ _Brassica rapa_ (turnip tops) & 0.14 \(\pm\) 0.04 & 0.87 \(\pm\) 0.59 & 8.06 \(\pm\) 3.80 & 71 \(\pm\) 22 & 24.2 \(\pm\) 9.9 & 29.9 \(\pm\) 9.1 \\ _Eruca veiscaria_ & 0.39 \(\pm\) 0.08 & 7.17 \(\pm\) 0.40 & 8.19 \(\pm\) 1.73 & 539 \(\pm\) 324 & 34.8 \(\pm\) 8.6 & 37.1 \(\pm\) 5.0 \\ \hline \multicolumn{6}{c}{**Farm II**} \\ _Brassica rapa_ (turnip greens) & 0.28 \(\pm\) 0.12 & 2.06 \(\pm\) 0.98 & 7.54 \(\pm\) 1.55 & 194 \(\pm\) 75 & 110.8 \(\pm\) 60.6 & 22.9 \(\pm\) 4.7 \\ _Brassica rapa_ (turnip tops) & 0.16 \(\pm\) 0.08 & 0.52 \(\pm\) 0.21 & 4.56 \(\pm\) 2.27 & 60 \(\pm\) 14 & 25.5 \(\pm\) 13.3 & 25.1 \(\pm\) 6.2 \\ _Eruca veiscaria_ & 0.26 \(\pm\) 0.09 & 3.29 \(\pm\) 1.72 & 9.33 \(\pm\) 1.30 & 413 \(\pm\) 175 & 33.2 \(\pm\) 8.0 & 34.2 \(\pm\) 4.5 \\ _Sinapis alba_ & \textless{}LOQ & 0.51 \(\pm\) 0.03 & 5.57 \(\pm\) 0.24 & 153 \(\pm\) 32 & 18.7 \(\pm\) 0.7 & 25.9 \(\pm\) 3.5 \\ \hline \multicolumn{6}{c}{**Organic**} \\ \hline _Brassica rapa_ (turnip greens) & 0.22 \(\pm\) 0.06 & 1.20 \(\pm\) 0.66 & 7.39 \(\pm\) 1.79 & 105 \(\pm\) 63 & 100.4 \(\pm\) 38.9 & 24.4 \(\pm\) 3.3 \\ _Brassica rapa_ (turnip tops) & 0.19 \(\pm\) 0.06 & 0.48 \(\pm\) 0.24 & 9.04 \(\pm\) 6.33 & 72 \(\pm\) 43 & 24.8 \(\pm\) 6.6 & 31.2 \(\pm\) 5.9 \\ _Eruca veiscaria_ & 0.44 \(\pm\) 0.11 & 5.17 \(\pm\) 2.25 & 10.2 \(\pm\) 1.1 & 700 \(\pm\) 207 & 48.1 \(\pm\) 9.8 & 33.0 \(\pm\) 3.0 \\ _Sinapis alba_ & \textless{}LOQ & 0.26 \(\pm\) 0.08 & 5.97 \(\pm\) 1.56 & 68 \(\pm\) 11 & 17.8 \(\pm\) 2.4 & 23.8 \(\pm\) 3.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Total trace elements concentration (dry matter) in _Brassicaceae_ species analyzed (mean \(\pm\) standard deviation). concentrations found in these _Brassicaceae_ species are in agreement with those reported by [PERSON] et al. [3] in a previous study (_Sinapis alba_ 20.8 ug/g d.w; _Eruca vesicaria_ 23.5 ug/g d.w). However, our work again failed to find statistically significant differences in the concentrations of these trace elements between organic and conventional agriculture. The results appearing in the bibliography do not show any clear trend for these trace elements either. [PERSON] et al. [19], in conventionally-grown carrots, have shown a higher content of Mn and Cu but a lower content of Zn than in organic ones. [PERSON] et al. [18], for organic lettuce, potato and carrot reported higher Cu contents than those in the same conventional vegetables. However, for conventional lettuce and carrot, higher Zn concentrations than those in the organic ones, were also found. On the other hand, although in our study no differences were found in Mn concentrations between conventionally-grown _Brassicas_ and organic ones, some authors have demonstrated that a lower mean concentration of Mn in organic crops is a common pattern. This could be due to the high concentrations of _arbuscular mycorrhizal fungi_ in organic soils [9; 20]. Although, this aspect has not been completely clarified. Other studies have shown that Mn is used as an additive to livestock feed supplements and, in turn, that this trace element would be present in the manure used in organic farming [9]. Co concentrations in turnip greens (_Brassicapa_) were very similar in the three studied conditions (Farm I conventional 0.23 ug/g d.w; Farm II conventional 0.28 ug/g d.w and Farm II organic 0.22 ug/g d.w, with no significant differences between them (Table 3). Regarding Cr contents in turnip greens, in organic plants harvested on Farm II, lower concentrations (1.20 ug/g d.w) (_p_ < 0.01) than in conventional ones of Farm I (2.41 ug/g d.w) and Farm II (2.06 ug/g d.w) were found.