Suitability of Different Cover Crop Mixtures and Seedlings for a New Tree Row Management in an Organic Orchard

In organic orchards disadvantages within the tree row weed management include tree damages, soil structure disturbance and humus erosion due to bare soil. As a solution to this problem the Sandwich system was developed at the Research Institute of Organic Agriculture (Frick, CH). Hereby the tree row is planted and strips right and left of the tree row are hoed mechanically. Grasses, legumes and grasses-legume mixtures were tested to identify suitable species for the tree row. Lolium perenne L., different Festuca species and subspecies, Poa pratensis L., Trifolium pratense L., Swiss and imported (i.e. European) ecotypes of Lotus corniculatus L. and Medicago lupulina L. were chosen. Additionally seedlings of Potentilla reptans L. and the allelopathic Hieracium pilosella L. were planted. Evenness, plant height and vegetation cover were monitored over one vegetation period. L. perenne turned out to be dominant; M. lupulina was more competitive as an imported ecotype whereas the reverse was shown for the Swiss ecotype of L. corniculatus in species-poor mixtures. The establishment of P. reptans was higher (nearly 100%) compared to H. pilosella. Both species showed the lowest height and due to these results future orchard tree row management research should focus on low-growing, stolon-building species.