Abstract The pattern of emergence, survival and mortality of six weed species and the dynamics of total weed population were studied for 2 years in potato fields under slash and burn (‘jhum’) and terrace cultivation in Meghalaya, northeast India. The composition of the weed flora in ‘jhum’ and terrace fields was similar, however, the population density was generally higher in the former. Weed seedlings appeared at three different times during both autumn and summer cropping seasons, giving rise to three distinct cohorts. The overall pattern of weed seedling emergence differed among cohorts and from species to species. The effect of cropping season on mortality patterns of seedling cohorts was not significant. For all weed species early cohorts showed high mortality during the 45 days after emergence, but in the third cohort mortality rate was almost constant throughout life. During the cropping period, seedling recruitment rate ( K) and fecundity rate ( F) were higher in terrace than in ‘jhum’, but the survivorship ( P) was greater in the latter. High annual rate of increase in weed seeds (λ) in soil and low seedling recruitment rate appear to be the main causes of larger weed-seed populations in ‘jhum’ fields compared with the terraces. The larger soil seed bank in ‘jhum’ than in terrace eventually contributed to a larger weed population in the former.