Fig. 4. NO3 and NH4 concentrations in soils after harvest of plants. NO3 concentrations were significantly influenced by the different soil types, char amendments and in the case of pyrochar also by fertilizer level as well as the presence of plants. For hydrochar, values on calcareous soil are shown separately for pots with and without plants because there were visible differences, however, these differences were not significant due to a high variance. The square in between shows the mean value for pots with and without plants. NH4 concentrations were only influenced by type of amendment and the presence of plants (Silage, hydrochar). Data are given with respective standard deviations. HTC: hydrochar, PC:pyrochar. Different letters and asterisks denote significant differences between treatments at a ¼ 0.05.