Abstract: To understand the effects of different tillage and fertilization modes on the weed growth in wheatmaize rotation system in North China Plain, an investigation was made on the no-tillage wheat field which is set up 5 years ago. No-tillage had a trend of decreasing the total density of weeds and the density of dominant species flixweed at the early stage of wheat growth, but the difference between traditional tillage and notillage was not significant. The weed biomass under no-tillage with straw remained and with straw removed decreased significantly, in which the flixweed biomass decreased by 57% and 73%, respectively, compared with that under traditional tillage. No-tillage also decreased the dry weight per flixweed plant by 27%-53%. Compared with conventional tillage, no-tillage with straw remained and with straw removed decreased the flixweed height by 25% and 19%, respectively. Generally, tillage mode had little effects on the growth of purple mustard and corn gromwell, while concentrated fertilizing decreased the total biomass of weeds by 21%-68%, flixweed biomass by 58%-65%, and corn gromwell biomass by 91%, compared with repeated fertilization. It was concluded that no-tillage could inhibit the growth of several weeds, while topdressing could promote the rapid growth of weeds.

Key words: Soil carbon/nitrogen cycle, Carbon density, Nitrogen cycle, C/N ratio