Dynamics of black-grass populations depending on the sowing time of winter wheat

Currently, economic, agronomic and environmental concerns, lead to reduce use of herbicides. This reduction can be help by cultural measures like delay of the sowing date. Four sowing dates of winter wheat from 15th of October to 26th of November were tested. Dynamic of black-grass populations and their reproduction rate were assessed as well as dynamic of winter wheat for each date. Delay of sowing could significantly reduce reproduction rate of blac-grass. It was shwn that the emergence rate (pl/m²), but also number of ears per plant and number of seeds per ear of black-grass decreased significantly with the sowing date. This reproduction of seeds productioin already is from sixty per cent of a delay of two weeks sowing.