## 3 Results and Discussion
### Changes in Soil Cu  
3.3.1. Changes of Cu Speciation  
The results of Cu speciation in soils with different soil management and of different soil properties are important to understand the mechanisms that can explain the changes in its bioavailability and mobility. The first acid-soluble step (Step 1) represents the most bioavailable and mobile fraction of Cu in the soils [62]. In our case (Table 2 and Figure S2), the highest values of Cu were released as expected from acidic soils (up to 10%). The average release of Cu was higher in acidic conventional soils, 16.4 mg kg\({}^{-1}\) (11.4%), compared to organic soils, 8.6 mg kg\({}^{-1}\) (6.6%). This difference can be explained because of the lower pH and, secondarily, because of the higher DOC of the acid conventional soil (Table 1). Significant Cu release was also detected in the calcareous organic soil (4.9 mg kg\({}^{-1}\), 3.8%) sampled in the Stajerska region. However, a very low release was detected in calcareous conventional soil sampled from Vipava Valley (1.1 mg kg\({}^{-1}\), 1.1%). Incubation for 6 months caused a significant decrease of this Cu fraction, but without differences whatever the temperature or moisture treatment. \begin{table}
\begin{tabular}{l l l l l l} \hline \multicolumn{2}{l}{**Soil Type/Management**} & \multicolumn{1}{c}{**Step 1**} & \multicolumn{1}{c}{**Step 2**} & \multicolumn{1}{c}{**Step 3**} & \multicolumn{1}{c}{**Step 4**} \\ \hline \multicolumn{2}{l}{Conventional} & \multicolumn{4}{c}{Cu (mg kg\({}^{-1}\))} \\ \cline{3-6} \multicolumn{2}{l}{} & Before incubation & 14.3 \(\pm\) 0.5 b  & 36.7 \(\pm\) 1.9 b  & 36.3 \(\pm\) 1.2 a  & 60.3 \(\pm\) 0.8 b  \\  & 19 \({}^{\circ}\)C 40\% WHC & 16.7 \(\pm\) 0.4 a  & 43.2 \(\pm\) 0.7 a  & 38.1 \(\pm\) 0.9 a  & 61.4 \(\pm\) 1.5 ab  \\  & 19 \({}^{\circ}\)C 10\% WHC & 16.8 \(\pm\) 0.6 a  & 42.1 \(\pm\) 2.0 a  & 38.1 \(\pm\) 0.6 a  & 61.8 \(\pm\) 0.7 ab  \\  & 29 \({}^{\circ}\)C 40\% WHC & 17.1 \(\pm\) 0.3 a  & 44.6 \(\pm\) 1.1 a  & 39.3 \(\pm\) 1.2 a  & 64.0 \(\pm\) 1.2 a  \\  & 29 \({}^{\circ}\)C 10\% WHC & 16.7 \(\pm\) 0.7 a  & 43.7 \(\pm\) 1.7 a  & 39.2 \(\pm\) 1.5 a  & 60.5 \(\pm\) 1.4 b  \\ \cline{3-6} \multicolumn{2}{l}{} & Organic & & & & \\ \cline{3-6} \multicolumn{2}{l}{} & Before incubation & 10.6 \(\pm\) 0.2 a  & 32.3 \(\pm\) 1.5 a  & 30.2 \(\pm\) 1.5 a  & 50.0 \(\pm\) 1.3 a  \\  & 19 \({}^{\circ}\)C 40\% WHC & 8.6 \(\pm\) 0.1 b  & 33.9 \(\pm\) 1.6 a  & 33.2 \(\pm\) 1.8 a  & 57.6 \(\pm\) 1.9 a  \\  & 19 \({}^{\circ}\)C 10\% WHC & 7.8 \(\pm\) 0.1 b  & 31.2 \(\pm\) 3.9 a  & 28.7 \(\pm\) 3.4 a  & 53.6 \(\pm\) 3.4 a  \\  & 29 \({}^{\circ}\)C 40\% WHC & 8.0 \(\pm\) 0.3 b  & 32.8 \(\pm\) 1.2 a  & 32.2 \(\pm\) 2.5 a  & 57.7 \(\pm\) 4.6 a  \\  & 29 \({}^{\circ}\)C 10\% WHC & 8.0 \(\pm\) 0.6 b  & 32.7 \(\pm\) 0.7 a  & 34.6 \(\pm\) 4.7 a  & 55.4 \(\pm\) 2.3 a  \\ \hline \multicolumn{2}{l}{} & Conventional & & & & \\ \cline{3-6} \multicolumn{2}{l}{} & Before incubation & 1.5 \(\pm\) 0.1 a  & 16.4 \(\pm\) 0.1 a  & 13.4 \(\pm\) 0.7 a  & 73.2 \(\pm\) 8.2 a  \\  & 19 \({}^{\circ}\)C 40\% WHC & 1.1 \(\pm\) 0.1 b  & 16.8 \(\pm\) 0.3 a  & 13.1 \(\pm\) 0.3 a  & 68.4 \(\pm\) 1.6 a  \\  & 19 \({}^{\circ}\)C 10\% WHC & 1.1 \(\pm\) 0.1 b  & 17.3 \(\pm\) 0.4 a  & 11.1 \(\pm\) 0.4 b  & 68.8 \(\pm\) 1.1 a  \\  & 29 \({}^{\circ}\)C 40\% WHC & 1.0 \(\pm\) 0.1 b  & 16.1 \(\pm\) 0.1 a  & 13.6 \(\pm\) 0.9 a  & 67.4 \(\pm\) 1.1 a  \\  & 29 \({}^{\circ}\)C 10\% WHC & 1.0 \(\pm\) 0.1 b  & 16.4 \(\pm\) 1.3 a  & 11 Iron and manganese oxides are also excellent scavengers of metals. In the reducible step (Step 2), levels of Cu released for both organic and conventional acidic soils were detectable (Table 2 and Figure S2). The average Cu levels released in Step 2 was 42.09 (29.4%) and 32.60 mg kg\({}^{-1}\) (24.8%) for conventional and organic acidic soils, respectively.