Performance of winter wheat varieties in white clover living mulch

Summary

The choice of variety for agricultural systems with multiple crops may differ from the one used in sole crop because of the changes in environmental conditions brought about by interspecific plant competition. Information about varietal performance under living mulch conditions as well as the suitability of the results of the official variety testing, conducted under conventional cropping conditions, for such systems is lacking for small grain cereals such as winter wheat (Triticum aestivum L.). In the current study, nine different winter wheat varieties were established in an existing living mulch of white clover (Trifolium repens L.) in three trials in the Swiss Midlands in the years 2003 and 2004. The winter wheat was directly sown in widely spaced rows (0.375 m) at a density of 450 viable grains m–2. Grain yield varied between 1.83 and 4.11 Mg ha–1. Plant height was correlated (r = 0.92, p < 0.001) with the grain yield, suggesting that varieties with long shoots may have an advantage because of the more ntense shading of the white clover plants.
However, the best yielding varieties were also those with the most intense tillering. Recorded values of grain quality traits (grain weight, test weight and protein content) for the tested varieties were analogous under the living mulch conditions of the current trials to those obtained in the official variety testing. This analogy was not observed for the grain yield, except for one trial, where the competitive strength of the white clover was reduced by mechanical interference prior to the seeding of the wheat, which positively affected tillering and hence grain yield. Thus, the use of better yielding varieties of winter wheat in living mulches is at the cost of decreased grain quality. The combination of yield and quality goals in living mulch systems will rather depend on the minimization of the competition of the cover crop on the wheat plants than on the variety choice following recommendations based on trials conducted under conventional cropping conditions.