Populational dynamics of pigweed (Amaranthus quitensis H.B.K.) effects of the chemical and mechanical treatments in a soybean plantation

Abstract

Trials have been conducted during 1986/87 y 1987/88 in order to describe the effect different agronomic pratices on pigweed (Amaranthus quitensis) population dynamics. Seedling recruitment, emergence fluxes, seedling survival, fecundity, initial and final seed banks and the annual rate of growth of the populations (l) with the two latter parameters were evaluated. Three pigweed emergence cohorts were evaluated. Seed production was only observed in first and second cohorts were evaluated. Seed production was higher density and greater number of seeds. Crop presence did not remarkably affect any the parameters considered. The l increased on average 53% in absence of the crop and 59% in presence of the crop when no chemical control and cultivation were performed. When a cultivation was done, l increase oscilated between 9 and 20% depending on the year. When herbicides were used, l shoved a population increase of 9% for postemergence applications and 28% for preemergence applications.