Abstract: The quantity of weeds depends on biotopic factors, on the supply of seeds in the soil and agrotechincal procedures, which stimulate or inhibit weed germination and development. Intercrop plants applied in contemporary systems, modifying the soil environment, also influence the weed infestation of crops. The aim of conducted studies was to determine the effect of intercrop plant application and kind of ploughing upon the state and degree of Spanish salsify weed infestation. In the field experiment with growing Spanish salsify (Scorzonera hispanica L.) the following intercrop plants were applied: common vetch (Vicia sativa L.), tansy phacelia (Phacelia tanacetifolia Benth.), oat (Avena sativa L.), as well as differentiated soil tillage: conventional plough cultivation with pre-winter mouldboard ploughing without intercrop; intercrop plant sowing plus deep pre-winter ploughing; intercrop plant sowing plus spring ploughing. In Spanish salsify weed infestation jointly 37 taxons of weeds were determined, among which the most numerously occurred: Chenopodium album L., Senecio vulgaris L., Capsella bursa-pastoris (L.) Med., Lamium amplexicaule L., Galinsoga ciliata (Raf.) S.F. Blake and Urtica urens L. The numerical force of primary and secondary Spanish salsify weed infestation after pre-winter and spring ploughing was similar. Intercrop plants significantly limited the primary and secondary weed infestation of this plant. The smallest quantities of weeds grew in objects where oat was the intercrop plant, and the largest – in cultivation without intercrops. Intercrop plants limited the occurrence of Senecio vulgaris and Capsella bursa-pastoris in primary weed infestation, and oats intercrop also limited the occurrence of Lamium amplexicaule and Senecio vulgaris in secondary weed infestation of Spanish salsify.

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