Einfluss von Intensität und Zeitpunkt der Bodenbearbeitung auf Ertragsbildung von Weizen und N-Dynamik in Wasserschutzgebieten

Summary

Water protection is controlled by specific regulations in the German Federal States, e.g. the SchALVO in Baden-Württemberg. An amendment of the SchALVO demands, amongst others, a changed timing and intensity of soil tillage directly after growing crops with high-nitrogen residues. As Organic Farming highly relies on soil tillage for weed control, there is concern about decrease of yield and increase of weed infesta-tion in water protection areas if tillage is restricted. Field experiments were performed on practical farms with three treatments according to SchALVO (rigid tine cultivator or mouldboard plough for primary tillage, used in October, December or February) and two treatments according to best management practice (mouldboard plough in Octo-ber or November). The treatments were combined with growing either winter wheat or spring wheat, depending on the date of tillage. There were no significant differences between the SchALVO and the practice-related treatments for yield, yield parameters, protein content and weed infestation, whereas there were differences between the winter crop and spring crop. The total Nmin in soil was slightly lower in the SchALVO treatments. Here, Nmin reached 39 – 42 kg Nmin ha-1 (mean of the experimental years), compared to the practice-related treatments with 42 or 43 kg Nmin ha-1 in the sub-experiment exemplarily presented in this paper. These differences were not significant at P ≤ 0.05. Mean Nmin was 38.5 kg ha-1 before starting the experiment. The lowest Nmin was found after using a cultivator in October. Since the one-time use of a cultiva-tor instead of the plough did not result in obvious disadvantages for the crop, the risk of yield reduction and increased weed infestation seems to be small. Nevertheless, if the initial number of perennial weeds, e.g. thistles, is high, a plough is supposed to be more effective for weed control than non-inversion tillage by cultivator.