Erträge und Bodenparameter nach 20 Jahren Direktsaat und Pflug

No-till and conventional plough tillage have been compared since 1994 in the Oberacker longterm field experiment at Inforama Ruetti in Zollikofen (Switzerland) on a slightly humic sandy loam soil. Crops were grown in a six-year crop rotation (peas, winter wheat, field beans, winter barley, sugarbeets and silage maize) in a strip trial with six adjoining plots. Twenty years into the trial, soil nutrient status was investigated and crop yields were statistically analysed. Soil was sampled layer-by-layer down to a depth of 50 cm, and analysed for soil organic carbon (Corg), total nitrogen content (Ntot), phosphorus (P), calcium (Ca), potassium (K) and magnesium (Mg) content, as well as pH and bulk density. Unlike in the conventional tillage system, Corg, Ntot, K and Mg were concentrated in the surface layer in the no-till system; in addition, the pH was lower and P and Ca had slight concentration maxima at around 20 cm depth. Although the distribution of Corg and nutrients differed significantly between no-till and conventional tillage, stocks of Corg and of all investigated nutrients were similar in both systems. The relative yield averaged over 20 years was 2.6% higher in no-till than in conventional tillage, but the difference was not significant. Winter cereals and legumes had significantly higher yields in the no-till system than in conventionally tilled soils. We conjecture that one of the reasons for the higher crop yields in no-till in the Oberacker long-term field experiment (since 2000 without potatoes) was the well-balanced crop rotation, including cover crops.