Assessment of weed infestation in winter wheat, winter triticale and spring barley cultivated since year 1998 in cereal crop rotation under three technologies varying in production intensity was conducted in years 2005, 2006 and 2007 at the Experimental Station Osiny (Institute of Soil Science and Plant Cultivation in Puławy). The degree of potential weed infestation (weed total dry matter per 1 m²) collected from areas protected against applied herbicides was evaluated, as well as herbicide efficacy. Generally, herbicide efficacy was very good or good. Potential weed infestation increased significantly as the intensity degree of production technology decreased. In 2006, the degree of potential weed infestation was generally much lower compared to 2005 and 2007 in particular under economical technology. In 2005 spring barley was the most infested by weeds and winter triticale was the least infested. In 2006, herbicide efficacy also was very good but generally all crops were less infested compared to 2005 and 2007. In 2007, winter wheat was the most infested by weeds, while spring barley was the least infested. The analysis of precipitation and monthly average temperature in spring does not give a logic answer why in 2006 weed infestation was so different compared to 2005 and 2007. Due to remarkable differences in potential weed infestation of tested crops grown under different technologies in 3-year period of study, it is impossible to give the final answer whether the changes in weed population and their total dry matter production depend on grain species grown under different cultivation technologies. It looks like the seed bank in soil is many times higher under economical production technology compared to intensive and integrated technologies.

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