Weed infestation depends on soil diaspore bank, the habitat conditions and the applied agricultural practices. Tillage constitutes one of the agrotechnical factors which significantly influence the condition and the level of weed infestation. In the conducted research, ploughless tillage practice and the application of herbicides considerably increased the number and the air-dry matter of weed populations per 1 m² of pea crop compared to plough tillage. It was also established that the number of weeds per 1 m² in the first term of weed infestation evaluation (in the phase of third true leaf) exceeded the number of weeds in the second term (ripening of pods and seeds). On the other hand, the air-dry matter of weeds was higher in the second term of evaluation. In addition, analyses revealed a higher number of weed species under the conditions of ploughless tillage (20–22 species) and herbicide application (20 species) than in the conventional tillage system (14–16 species). The predominant species under the conditions of conventional tillage were: Amaranthus retroflexus L. and Echinochloa crus-galli (L.) P.B. (in the first term of evaluation), and Avena fatua L. and Chenopodium album L. (in the second term). The predominant species in the ploughless tillage were: Echinochloa crus-galli (L.) P.B. and Amaranthus retroflexus L. (in the first term) as well as Fallopia convolvulus (L.) A. Löve, Avena fatua L. and Galinsoga praviflora Cav. (in the second term). In case of herbicide application, the prevailing species were: Echinochloa crus-galli (L.) P.B. and Matricaria inodora L. (in the first term) as well as Matricaria inodora L. and Echinochloa crus-galli (L.) P.B. (in the second term). The reduced tillage increased the number of perennial weeds: Cirsium arvense (L.) Scop., Elymus repens (L.) P.B. and Convolvulus arvensis L.

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