Influence of ridge cultivation and phacelia intercrop on weed infestation of root vegetables of the Asteraceae family

The field experiment focused on three high-inulin vegetable crops: chicory (Cichorium intybus L. var. sativum Bisch), black salsify (Scorzonera hispanica L.) and common salsify (Tragopogon porrifolius L.), and took into account two cultivation methods (flat soil and ridges) and a phacelia (Phacelia tanacetifolia L.) intercrop, the biomass of which was mixed with the soil during pre-winter ploughing. Cultivation without an intercrop served as the control. The studies aimed at evaluating the influence of ridge cultivation using a phacelia intercrop on the species composition and population of vegetable weeds as compared to traditional flat-soil cultivation with no intercrop. In total, 24 taxa in the primary and 31 taxa in the secondary weed populations (mostly characteristic for vegetable crops) were recorded in high-inulin species plantations. Monocarpic species such as Senecio vulgaris, Chenopodium album and Lamium amplexicaule dominated in the spring, while Stellaria media, Capsella bursa-pastoris and Urtica urens were most numerous at the end of the vegetation period. Applying phacelia as the intercrop and ploughing its biomass before winter significantly reduced the primary weed population for all of the cultivated crop species as compared to the no-intercrop cultivations. Phacelia grown as the intercrop reduced the occurrence of Senecio vulgaris, while favouring the development of Lamium amplexicaule. The cultivation system affected the primary weed infestation of vegetables, whereas it had no impact on the level of secondary weed infestation. At the beginning of the vegetation periods, fewer weeds grew in ridges than in the flat soil system. The crop species had no effect on the primary weed infestation, while it influenced weed numbers in the secondary. The lowest number of weeds was recorded in the secondary weed infestation of chicory, the well-developed leaf rosettes of which efficiently eliminated most of the weeds.