The paper presents the results of a 6-year investigation in a crop-rotation experiment on lessive soil (Orthic Luvisols) of a good wheat complex and of a very good rye complex. There was evaluated yielding of field pea cultivars, Ergo and Agat, grown in a 6-field crop rotation and an increasing 1-6 year monoculture with three pea protection variants. The field pea seed yield in the crop rotation amounted to an average of 3.99 t∙ha^-1, while in the continuous cropping – it was 47% lower. In monoculture there was a decrease in the plant density by 12.1%, the number of pods by 44.2% and the number and 1000 seed weight by 48.9 and by 21.9%, respectively. The field pea cultivars reacted similarly to both the kind of crop sequence (crop rotation, monoculture) and the crop protection levels (herbicides, fungicides). The application of herbicides and fungicides in crop rotation is not justifiable, while in monoculture it increases the seed yield.

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