Growth, yield, and yield components of winter wheat and the effects of tillage intensity, preceding crops, and N fertilisation

Conservation tillage is widely practiced in semi-arid climates, mostly in small grain crop rotations. It is implemented to a much lesser extent in cool and humid climates of Europe, mainly due to a lack of knowledge about agronomic and ecological impacts. This study was conducted in light- to medium-textured soils in the Swiss midlands from 1995 to 2000. The aim was to determine whether tillage intensity impacted wheat yield and measure the effects of the preceding crop and the level of N fertilisation. Conventional tillage (CT) with ploughing, minimum tillage (MT) with a chisel, and no-tillage (NT) were studied in the following crop rotation: winter wheat (Triticum aestivum L.)–oilseed rape (Brassica napus L.)–winter wheat–maize (Zea mays L.). Winter wheat was grown at either 0 kg N ha−1 (N0) or at the recommended N supply (N1). Harvest residues of all the crops were left on the field. In the early stages wheat development under NT was slightly slower than under CT and MT, but at maturity the shoot biomass was 2% higher under NT than under the other tillages. The grain yield decreased by 3% under NT compared to CT and MT, mainly due to fewer ears per area and a significantly lower thousand-kernel weight. Wheat planted after oilseed rape had significantly higher shoot biomass and grain yield than wheat planted after maize. At the beginning of the vegetation season there were small but significant differences in the soil mineral N content among the tillage treatments. Accordingly, the level of N fertiliser applied was adjusted to ensure similar N availability in all tillage systems. The relative reduction in grain yield under NT compared to CT and MT was similar with and without N fertilisation. Thus, N availability was not a limiting factor for the yield of NT wheat in this study.