Abstract:A terminology of Eco-economic period threshold for weed control" was proposed, on this basis, field experiments were conducted during 1984 and 1985 in Beijing region to fit the functional relationships between the relative weedy or weedfree days of Echinochloa crus-gal-li and the relative yield of summer soybeans. Finally,calculating models of the eco-economic period threshold for controlling the wd were established.Results calculated by using these models showed that the eco-economic period threshold for ...