EN
The reaction of spring barley to 38–47-year monoculture carried out in 10-year studies (2005–2014) on albic luvisol soil at the Production and Experimental Station in Bałcyny near Ostróda town in different conditions of chemical protection has been presented. The following chemical protections of a barley canopy: 0 – without protection; H – protection from weeds and HF – protection from weeds and diseases have been considered. The cultivation of spring barley in 6-field crop rotation: sugar beet – maize – spring barley – pea – winter rape – winter wheat was as a comparative object. In a crop rotation the average yield of spring barley grain amounted to 6.88 t ha-1. The cultivation in 38–47-year monoculture has decreased its yielding on average by 20.4%. The biggest decrease of its productivity took place on the object without protection – 27.5%. The application of herbicides has limited the decrease to 17.5% while combined application of herbicides and fungicides up to 16.5%. Less decrease is the result of plant protection products higher efficacy in monoculture than in a crop rotation. Herbicides on that field has increased spring barley yield on average by 17.9%, the combined application of fungicides and herbicides by 24.8% while in the case of a crop rotation by 3.6 and 8.3% respectively. Worse yielding of spring barley in a monoculture are conditioned by thinning out density of ears per 1 m2, and the decrease of grains weight from an ear and the weight of 1.000 grain