Effects of reduced tillage, fertilisation and biodynamic preparations on crop yield, weed infestation and the occurrence of toxigenic fusaria.

In a recently started long-term field trial (2002-2011), located in Frick (1000 mm mean annual precipi-tation) near Basle (Switzerland), the effect of reduced tillage on crop yield, weed infestation, and oc-currence of toxigenic fusaria was studied on a heavy soil (45% clay) in a crop rotation under organic farming conditions. Here, we present results of the first two experimental years (2003-2004), which are considered as the conversion period. Wheat yield was 16% higher (p < 0.001) in ploughed plots than in the plots with reduced tillage (chisel and rotary harrow). In the following year, sunflower yield was enhanced by 5% (p = 0.06) in reduced tilled plots. Reduced tilled plots manifested a higher weed infestation, in particular with Convolvulus arvensis and Stellaria media. With the exception of low levels of Fusarium poae, no toxigenic fusaria were detected in wheat grains possibly due to the excep-tionally dry and hot summer 2003. The deoxynivalenol (DON) content was low in all treatments. While the DON content in wheat straw was increased after reduced tillage, it was decreased after ap-plication of biodynamic preparations (p < 0.05). Overall, we assume that even on heavy soils, reduced tillage systems may be applicable on organic farms, but with a considerably higher input of labour.