Weed Occurrence in a Young Apple Orchard Mulched With Two Different Organic Materials

In this study, conducted at the Research Station of the Wrocław University of Environmental and Life Sciences, Poland, we sought to determine the communities of weed species and their temporal occurrence in a young apple orchard mulched with spent mushroom compost or Miscanthus straw applied to tree rows. A herbicide fallow treatment was used as a control. During the first year of application, both organic mulches protected against the germination of weed seeds stored within the soil. In subsequent years, however, annual weeds occurred in the mulched tree rows, the most aggressive of which was Chenopodium album L. Annual increases in population densities were noted over the 4 subsequent years of research, particularly in the rows receiving spent mushroom compost. Perennial species in the family Poaceae and genus Malva were present in soil receiving both organic mulches. Trifolium repens L. was the perennial weed most often noted in the Miscanthus mulch, whereas Taraxacum officinale Web. was more characteristic of the spent mushroom compost. Commencing from the spring of the third year following apple tree planting, weed infestation associated with the spent mushroom compost was similar to that observed in the herbicide fallow, thus necessitating three annual applications of herbicide to further maintain the orchard. The insufficient weed suppression obtained with this mulch precludes its recommendation as an effective weed management system. Although Miscanthus straw provided extended tree row protection from weed infestation, herbicide intervention was also required. Notably, however, despite the fact that Miscanthus straw provided conditions more favorable to tree growth, apple tree yields and fruit quality tended to be similar under the three investigated orchard soil management systems.