Comparative Analysis of Undersown Cover Crops and Bio-Preparations on Weed Spread and Organically Grown Spring Oilseed Rape Yield

Abstract

Undersown cover crops are an important tool for weed control in organic farming. The hypothesis of this research was that undersown crimson (incarnate) clover (Trifolium incarnatum Broth.), hairy (winter) vetch (Vicia villosa Roth.), perennial ryegrass (Lolium perenne L.), and winter rye (Secale cereale L.) in combination with bio-preparations inhibit the spread of weeds and influence the seed yield of spring oilseed rape in organic farming. The dry biomass of undersown cover crops, as well as the number and dry biomass of weeds, were determined before harvesting spring oilseed rape (Brassica napus L. spp. oleifera biennis Metzg.) (main crop) to identify the underlying influences on seed yield. We summarized that hairy vetch was distinguished by its rapid growth and by the fact that it produced an aboveground dry biomass that was significantly higher (1.9 to 12.4 times) compared with other cover crops, while crimson clover grown as a cover crop had a significantly higher aboveground dry biomass (by a factor of 3.2 to 4.9) compared with that of perennial ryegrass and winter rye. During the spring oilseed growing season, undersown cover crops did not suppress early emerging weeds that had not been controlled by inter-row loosening. During the spring growing season, weeds were best suppressed using bio-preparation-treated perennial ryegrass. The highest oilseed rape seed yield was obtained in 2020 after the application of bio-preparations in plots without any cover crops. Perennial ryegrass as a cover crop in combination with bio-preparations produced the highest reduction in oilseed rape seed yield. Further research should be directed toward determining the long-term effects of cover crops and bio-preparations on plant community formation in organic farming.